diff --git a/bin/configs/rust-reqwest-nullable-enum-query-params.yaml b/bin/configs/rust-reqwest-nullable-enum-query-params.yaml
new file mode 100644
index 000000000000..9dcee7df4ad9
--- /dev/null
+++ b/bin/configs/rust-reqwest-nullable-enum-query-params.yaml
@@ -0,0 +1,8 @@
+generatorName: rust
+outputDir: samples/client/others/rust/reqwest/nullable-enum-query-params
+library: reqwest
+inputSpec: modules/openapi-generator/src/test/resources/3_1/rust/nullable-enum-query-params.yaml
+templateDir: modules/openapi-generator/src/main/resources/rust
+additionalProperties:
+  supportAsync: true
+  packageName: nullable-enum-query-params-reqwest
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustClientCodegen.java
index 7f42d081ed00..3c70fb2b73b2 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustClientCodegen.java
@@ -774,19 +774,18 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         boolean useAsyncFileStream = false;
         List<CodegenOperation> operations = objectMap.getOperation();
         for (CodegenOperation operation : operations) {
-            if (operation.pathParams != null && operation.pathParams.size() > 0) {
-
-                // For types with `isAnyType` we assume it's a `serde_json::Value` type.
-                // However for path, query, and headers it's unlikely to be JSON so we default to `String`.
-                // Note that we keep the default `serde_json::Value` for body parameters.
-                for (var param : operation.allParams) {
-                    if (param.isAnyType && (param.isPathParam || param.isQueryParam || param.isHeaderParam)) {
-                        param.dataType = "String";
-                        param.isPrimitiveType = true;
-                        param.isString = true;
-                    }
+            // For types with `isAnyType` we assume it's a `serde_json::Value` type.
+            // However for path, query, and headers it's unlikely to be JSON so we default to `String`.
+            // Note that we keep the default `serde_json::Value` for body parameters.
+            for (var param : operation.allParams) {
+                if (param.isAnyType && (param.isPathParam || param.isQueryParam || param.isHeaderParam)) {
+                    param.dataType = "String";
+                    param.isPrimitiveType = true;
+                    param.isString = true;
                 }
+            }
 
+            if (operation.pathParams != null && operation.pathParams.size() > 0) {
                 for (var pathParam : operation.pathParams) {
                     if (!pathParam.baseName.contains("-")) {
                         continue;
diff --git a/modules/openapi-generator/src/test/resources/3_1/rust/nullable-enum-query-params.yaml b/modules/openapi-generator/src/test/resources/3_1/rust/nullable-enum-query-params.yaml
new file mode 100644
index 000000000000..57ac7d4d75e5
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_1/rust/nullable-enum-query-params.yaml
@@ -0,0 +1,88 @@
+openapi: 3.1.0
+info:
+  title: Nullable Enum Query Parameter Test
+  description: >-
+    Test spec for enum query parameters whose schema is not a bare $ref, as
+    emitted by FastAPI and other 3.1 producers. The same operation is defined
+    with and without a path parameter, because the two used to be generated
+    differently.
+  version: 1.0.0
+paths:
+  /widgets/summary:
+    get:
+      operationId: getWidgetSummary
+      summary: Get a widget summary
+      parameters:
+        - name: kind
+          in: query
+          description: Kind filter, expressed as an anyOf with null
+          required: false
+          schema:
+            anyOf:
+              - $ref: '#/components/schemas/WidgetKind'
+              - type: 'null'
+            title: Kind
+        - name: sort
+          in: query
+          description: Sort order, expressed as a $ref with sibling keywords
+          required: false
+          schema:
+            $ref: '#/components/schemas/SortDirection'
+            title: Sort
+      responses:
+        '200':
+          description: Successful response
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/WidgetSummary'
+  /widgets/{widget_id}/summary:
+    get:
+      operationId: getWidgetSummaryById
+      summary: Get a widget summary for a single widget
+      parameters:
+        - name: widget_id
+          in: path
+          required: true
+          schema:
+            type: string
+        - name: kind
+          in: query
+          description: Kind filter, expressed as an anyOf with null
+          required: false
+          schema:
+            anyOf:
+              - $ref: '#/components/schemas/WidgetKind'
+              - type: 'null'
+            title: Kind
+      responses:
+        '200':
+          description: Successful response
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/WidgetSummary'
+components:
+  schemas:
+    WidgetKind:
+      type: string
+      description: Widget kind
+      enum:
+        - basic
+        - premium
+    SortDirection:
+      type: string
+      description: Sort direction options
+      enum:
+        - asc
+        - desc
+    WidgetSummary:
+      type: object
+      properties:
+        kind:
+          $ref: '#/components/schemas/WidgetKind'
+        total:
+          type: integer
+      required:
+        - kind
+        - total
diff --git a/samples/client/others/rust/Cargo.lock b/samples/client/others/rust/Cargo.lock
index 4e2285a69629..04b5af7b9803 100644
--- a/samples/client/others/rust/Cargo.lock
+++ b/samples/client/others/rust/Cargo.lock
@@ -867,6 +867,17 @@ dependencies = [
  "tempfile",
 ]
 
+[[package]]
+name = "nullable-enum-query-params-reqwest"
+version = "1.0.0"
+dependencies = [
+ "reqwest 0.13.1",
+ "serde",
+ "serde_json",
+ "serde_repr",
+ "url",
+]
+
 [[package]]
 name = "num_cpus"
 version = "1.17.0"
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/.gitignore b/samples/client/others/rust/reqwest/nullable-enum-query-params/.gitignore
new file mode 100644
index 000000000000..6aa106405a4b
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/.gitignore
@@ -0,0 +1,3 @@
+/target/
+**/*.rs.bk
+Cargo.lock
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator-ignore b/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator-ignore
new file mode 100644
index 000000000000..7484ee590a38
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator-ignore
@@ -0,0 +1,23 @@
+# OpenAPI Generator Ignore
+# Generated by openapi-generator https://github.com/openapitools/openapi-generator
+
+# Use this file to prevent files from being overwritten by the generator.
+# The patterns follow closely to .gitignore or .dockerignore.
+
+# As an example, the C# client generator defines ApiClient.cs.
+# You can make changes and tell OpenAPI Generator to ignore just this file by uncommenting the following line:
+#ApiClient.cs
+
+# You can match any string of characters against a directory, file or extension with a single asterisk (*):
+#foo/*/qux
+# The above matches foo/bar/qux and foo/baz/qux, but not foo/bar/baz/qux
+
+# You can recursively match patterns against a directory, file or extension with a double asterisk (**):
+#foo/**/qux
+# This matches foo/bar/qux, foo/baz/qux, and foo/bar/baz/qux
+
+# You can also negate patterns with an exclamation (!).
+# For example, you can ignore all files in a docs folder with the file extension .md:
+#docs/*.md
+# Then explicitly reverse the ignore rule for a single file:
+#!docs/README.md
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator/FILES b/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator/FILES
new file mode 100644
index 000000000000..72cd90e9aedf
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator/FILES
@@ -0,0 +1,18 @@
+.gitignore
+.openapi-generator-ignore
+.travis.yml
+Cargo.toml
+README.md
+docs/DefaultApi.md
+docs/SortDirection.md
+docs/WidgetKind.md
+docs/WidgetSummary.md
+git_push.sh
+src/apis/configuration.rs
+src/apis/default_api.rs
+src/apis/mod.rs
+src/lib.rs
+src/models/mod.rs
+src/models/sort_direction.rs
+src/models/widget_kind.rs
+src/models/widget_summary.rs
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator/VERSION b/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator/VERSION
new file mode 100644
index 000000000000..8fc8df61083a
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/.openapi-generator/VERSION
@@ -0,0 +1 @@
+7.25.0-SNAPSHOT
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/.travis.yml b/samples/client/others/rust/reqwest/nullable-enum-query-params/.travis.yml
new file mode 100644
index 000000000000..22761ba7ee19
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/.travis.yml
@@ -0,0 +1 @@
+language: rust
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/Cargo.toml b/samples/client/others/rust/reqwest/nullable-enum-query-params/Cargo.toml
new file mode 100644
index 000000000000..c49a8bce2e25
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "nullable-enum-query-params-reqwest"
+version = "1.0.0"
+authors = ["OpenAPI Generator team and contributors"]
+description = "Test spec for enum query parameters whose schema is not a bare $ref, as emitted by FastAPI and other 3.1 producers. The same operation is defined with and without a path parameter, because the two used to be generated differently."
+# Override this license by providing a License Object in the OpenAPI.
+license = "Unlicense"
+edition = "2021"
+
+[dependencies]
+serde = { version = "^1.0", features = ["derive"] }
+serde_json = "^1.0"
+serde_repr = "^0.1"
+url = "^2.5"
+reqwest = { version = "^0.13", default-features = false, features = ["json", "multipart", "query", "form"] }
+
+[features]
+default = ["native-tls"]
+native-tls = ["reqwest/native-tls"]
+rustls = ["reqwest/rustls"]
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/README.md b/samples/client/others/rust/reqwest/nullable-enum-query-params/README.md
new file mode 100644
index 000000000000..ac643b61d663
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/README.md
@@ -0,0 +1,49 @@
+# Rust API client for nullable-enum-query-params-reqwest
+
+Test spec for enum query parameters whose schema is not a bare $ref, as emitted by FastAPI and other 3.1 producers. The same operation is defined with and without a path parameter, because the two used to be generated differently.
+
+
+## Overview
+
+This API client was generated by the [OpenAPI Generator](https://openapi-generator.tech) project.  By using the [openapi-spec](https://openapis.org) from a remote server, you can easily generate an API client.
+
+- API version: 1.0.0
+- Package version: 1.0.0
+- Generator version: 7.25.0-SNAPSHOT
+- Build package: `org.openapitools.codegen.languages.RustClientCodegen`
+
+## Installation
+
+Put the package under your project folder in a directory named `nullable-enum-query-params-reqwest` and add the following to `Cargo.toml` under `[dependencies]`:
+
+```
+nullable-enum-query-params-reqwest = { path = "./nullable-enum-query-params-reqwest" }
+```
+
+## Documentation for API Endpoints
+
+All URIs are relative to *http://localhost*
+
+Class | Method | HTTP request | Description
+------------ | ------------- | ------------- | -------------
+*DefaultApi* | [**get_widget_summary**](docs/DefaultApi.md#get_widget_summary) | **GET** /widgets/summary | Get a widget summary
+*DefaultApi* | [**get_widget_summary_by_id**](docs/DefaultApi.md#get_widget_summary_by_id) | **GET** /widgets/{widget_id}/summary | Get a widget summary for a single widget
+
+
+## Documentation For Models
+
+ - [SortDirection](docs/SortDirection.md)
+ - [WidgetKind](docs/WidgetKind.md)
+ - [WidgetSummary](docs/WidgetSummary.md)
+
+
+To get access to the crate's generated documentation, use:
+
+```
+cargo doc --open
+```
+
+## Author
+
+
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/DefaultApi.md b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/DefaultApi.md
new file mode 100644
index 000000000000..10e9f6bcb6da
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/DefaultApi.md
@@ -0,0 +1,68 @@
+# \DefaultApi
+
+All URIs are relative to *http://localhost*
+
+Method | HTTP request | Description
+------------- | ------------- | -------------
+[**get_widget_summary**](DefaultApi.md#get_widget_summary) | **GET** /widgets/summary | Get a widget summary
+[**get_widget_summary_by_id**](DefaultApi.md#get_widget_summary_by_id) | **GET** /widgets/{widget_id}/summary | Get a widget summary for a single widget
+
+
+
+## get_widget_summary
+
+> models::WidgetSummary get_widget_summary(kind, sort)
+Get a widget summary
+
+### Parameters
+
+
+Name | Type | Description  | Required | Notes
+------------- | ------------- | ------------- | ------------- | -------------
+**kind** | Option<**String**> | Kind filter, expressed as an anyOf with null |  |
+**sort** | Option<**String**> | Sort order, expressed as a $ref with sibling keywords |  |
+
+### Return type
+
+[**models::WidgetSummary**](WidgetSummary.md)
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: application/json
+
+[[Back to top]](#) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to Model list]](../README.md#documentation-for-models) [[Back to README]](../README.md)
+
+
+## get_widget_summary_by_id
+
+> models::WidgetSummary get_widget_summary_by_id(widget_id, kind)
+Get a widget summary for a single widget
+
+### Parameters
+
+
+Name | Type | Description  | Required | Notes
+------------- | ------------- | ------------- | ------------- | -------------
+**widget_id** | **String** |  | [required] |
+**kind** | Option<**String**> | Kind filter, expressed as an anyOf with null |  |
+
+### Return type
+
+[**models::WidgetSummary**](WidgetSummary.md)
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: application/json
+
+[[Back to top]](#) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to Model list]](../README.md#documentation-for-models) [[Back to README]](../README.md)
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/SortDirection.md b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/SortDirection.md
new file mode 100644
index 000000000000..a889d395b025
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/SortDirection.md
@@ -0,0 +1,13 @@
+# SortDirection
+
+## Enum Variants
+
+| Name | Value |
+|---- | -----|
+| Asc | asc |
+| Desc | desc |
+
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/WidgetKind.md b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/WidgetKind.md
new file mode 100644
index 000000000000..638d41981138
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/WidgetKind.md
@@ -0,0 +1,13 @@
+# WidgetKind
+
+## Enum Variants
+
+| Name | Value |
+|---- | -----|
+| Basic | basic |
+| Premium | premium |
+
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/WidgetSummary.md b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/WidgetSummary.md
new file mode 100644
index 000000000000..3ef8da8c5b86
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/docs/WidgetSummary.md
@@ -0,0 +1,12 @@
+# WidgetSummary
+
+## Properties
+
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**kind** | [**models::WidgetKind**](WidgetKind.md) |  | 
+**total** | **i32** |  | 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/git_push.sh b/samples/client/others/rust/reqwest/nullable-enum-query-params/git_push.sh
new file mode 100644
index 000000000000..f53a75d4fabe
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/git_push.sh
@@ -0,0 +1,57 @@
+#!/bin/sh
+# ref: https://help.github.com/articles/adding-an-existing-project-to-github-using-the-command-line/
+#
+# Usage example: /bin/sh ./git_push.sh wing328 openapi-petstore-perl "minor update" "gitlab.com"
+
+git_user_id=$1
+git_repo_id=$2
+release_note=$3
+git_host=$4
+
+if [ "$git_host" = "" ]; then
+    git_host="github.com"
+    echo "[INFO] No command line input provided. Set \$git_host to $git_host"
+fi
+
+if [ "$git_user_id" = "" ]; then
+    git_user_id="GIT_USER_ID"
+    echo "[INFO] No command line input provided. Set \$git_user_id to $git_user_id"
+fi
+
+if [ "$git_repo_id" = "" ]; then
+    git_repo_id="GIT_REPO_ID"
+    echo "[INFO] No command line input provided. Set \$git_repo_id to $git_repo_id"
+fi
+
+if [ "$release_note" = "" ]; then
+    release_note="Minor update"
+    echo "[INFO] No command line input provided. Set \$release_note to $release_note"
+fi
+
+# Initialize the local directory as a Git repository
+git init
+
+# Adds the files in the local repository and stages them for commit.
+git add .
+
+# Commits the tracked changes and prepares them to be pushed to a remote repository.
+git commit -m "$release_note"
+
+# Sets the new remote
+git_remote=$(git remote)
+if [ "$git_remote" = "" ]; then # git remote not defined
+
+    if [ "$GIT_TOKEN" = "" ]; then
+        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git credential in your environment."
+        git remote add origin https://${git_host}/${git_user_id}/${git_repo_id}.git
+    else
+        git remote add origin https://${git_user_id}:"${GIT_TOKEN}"@${git_host}/${git_user_id}/${git_repo_id}.git
+    fi
+
+fi
+
+git pull origin master
+
+# Pushes (Forces) the changes in the local repository up to the remote repository
+echo "Git pushing to https://${git_host}/${git_user_id}/${git_repo_id}.git"
+git push origin master 2>&1 | grep -v 'To https'
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/configuration.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/configuration.rs
new file mode 100644
index 000000000000..e940c244d748
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/configuration.rs
@@ -0,0 +1,51 @@
+/*
+ * Nullable Enum Query Parameter Test
+ *
+ * Test spec for enum query parameters whose schema is not a bare $ref, as emitted by FastAPI and other 3.1 producers. The same operation is defined with and without a path parameter, because the two used to be generated differently.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ * Generated by: https://openapi-generator.tech
+ */
+
+
+
+#[derive(Debug, Clone)]
+pub struct Configuration {
+    pub base_path: String,
+    pub user_agent: Option<String>,
+    pub client: reqwest::Client,
+    pub basic_auth: Option<BasicAuth>,
+    pub oauth_access_token: Option<String>,
+    pub bearer_access_token: Option<String>,
+    pub api_key: Option<ApiKey>,
+}
+
+pub type BasicAuth = (String, Option<String>);
+
+#[derive(Debug, Clone)]
+pub struct ApiKey {
+    pub prefix: Option<String>,
+    pub key: String,
+}
+
+
+impl Configuration {
+    pub fn new() -> Configuration {
+        Configuration::default()
+    }
+}
+
+impl Default for Configuration {
+    fn default() -> Self {
+        Configuration {
+            base_path: "http://localhost".to_owned(),
+            user_agent: Some("OpenAPI-Generator/1.0.0/rust".to_owned()),
+            client: reqwest::Client::new(),
+            basic_auth: None,
+            oauth_access_token: None,
+            bearer_access_token: None,
+            api_key: None,
+        }
+    }
+}
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/default_api.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/default_api.rs
new file mode 100644
index 000000000000..e05366d129e8
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/default_api.rs
@@ -0,0 +1,115 @@
+/*
+ * Nullable Enum Query Parameter Test
+ *
+ * Test spec for enum query parameters whose schema is not a bare $ref, as emitted by FastAPI and other 3.1 producers. The same operation is defined with and without a path parameter, because the two used to be generated differently.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ * Generated by: https://openapi-generator.tech
+ */
+
+
+use reqwest;
+use serde::{Deserialize, Serialize, de::Error as _};
+use crate::{apis::ResponseContent, models};
+use super::{Error, configuration, ContentType};
+
+
+/// struct for typed errors of method [`get_widget_summary`]
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum GetWidgetSummaryError {
+    UnknownValue(serde_json::Value),
+}
+
+/// struct for typed errors of method [`get_widget_summary_by_id`]
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum GetWidgetSummaryByIdError {
+    UnknownValue(serde_json::Value),
+}
+
+
+pub async fn get_widget_summary(configuration: &configuration::Configuration, kind: Option<&str>, sort: Option<&str>) -> Result<models::WidgetSummary, Error<GetWidgetSummaryError>> {
+    // add a prefix to parameters to efficiently prevent name collisions
+    let p_query_kind = kind;
+    let p_query_sort = sort;
+
+    let uri_str = format!("{}/widgets/summary", configuration.base_path);
+    let mut req_builder = configuration.client.request(reqwest::Method::GET, &uri_str);
+
+    if let Some(ref param_value) = p_query_kind {
+        req_builder = req_builder.query(&[("kind", &param_value.to_string())]);
+    }
+    if let Some(ref param_value) = p_query_sort {
+        req_builder = req_builder.query(&[("sort", &param_value.to_string())]);
+    }
+    if let Some(ref user_agent) = configuration.user_agent {
+        req_builder = req_builder.header(reqwest::header::USER_AGENT, user_agent.clone());
+    }
+
+    let req = req_builder.build()?;
+    let resp = configuration.client.execute(req).await?;
+
+    let status = resp.status();
+    let content_type = resp
+        .headers()
+        .get("content-type")
+        .and_then(|v| v.to_str().ok())
+        .unwrap_or("application/octet-stream");
+    let content_type = super::ContentType::from(content_type);
+
+    if !status.is_client_error() && !status.is_server_error() {
+        let content = resp.text().await?;
+        match content_type {
+            ContentType::Json => serde_json::from_str(&content).map_err(Error::from),
+            ContentType::Text => return Err(Error::from(serde_json::Error::custom("Received `text/plain` content type response that cannot be converted to `models::WidgetSummary`"))),
+            ContentType::Unsupported(unknown_type) => return Err(Error::from(serde_json::Error::custom(format!("Received `{unknown_type}` content type response that cannot be converted to `models::WidgetSummary`")))),
+        }
+    } else {
+        let content = resp.text().await?;
+        let entity: Option<GetWidgetSummaryError> = serde_json::from_str(&content).ok();
+        Err(Error::ResponseError(ResponseContent { status, content, entity }))
+    }
+}
+
+pub async fn get_widget_summary_by_id(configuration: &configuration::Configuration, widget_id: &str, kind: Option<&str>) -> Result<models::WidgetSummary, Error<GetWidgetSummaryByIdError>> {
+    // add a prefix to parameters to efficiently prevent name collisions
+    let p_path_widget_id = widget_id;
+    let p_query_kind = kind;
+
+    let uri_str = format!("{}/widgets/{widget_id}/summary", configuration.base_path, widget_id=crate::apis::urlencode(p_path_widget_id));
+    let mut req_builder = configuration.client.request(reqwest::Method::GET, &uri_str);
+
+    if let Some(ref param_value) = p_query_kind {
+        req_builder = req_builder.query(&[("kind", &param_value.to_string())]);
+    }
+    if let Some(ref user_agent) = configuration.user_agent {
+        req_builder = req_builder.header(reqwest::header::USER_AGENT, user_agent.clone());
+    }
+
+    let req = req_builder.build()?;
+    let resp = configuration.client.execute(req).await?;
+
+    let status = resp.status();
+    let content_type = resp
+        .headers()
+        .get("content-type")
+        .and_then(|v| v.to_str().ok())
+        .unwrap_or("application/octet-stream");
+    let content_type = super::ContentType::from(content_type);
+
+    if !status.is_client_error() && !status.is_server_error() {
+        let content = resp.text().await?;
+        match content_type {
+            ContentType::Json => serde_json::from_str(&content).map_err(Error::from),
+            ContentType::Text => return Err(Error::from(serde_json::Error::custom("Received `text/plain` content type response that cannot be converted to `models::WidgetSummary`"))),
+            ContentType::Unsupported(unknown_type) => return Err(Error::from(serde_json::Error::custom(format!("Received `{unknown_type}` content type response that cannot be converted to `models::WidgetSummary`")))),
+        }
+    } else {
+        let content = resp.text().await?;
+        let entity: Option<GetWidgetSummaryByIdError> = serde_json::from_str(&content).ok();
+        Err(Error::ResponseError(ResponseContent { status, content, entity }))
+    }
+}
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/mod.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/mod.rs
new file mode 100644
index 000000000000..fdcc89b36066
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/apis/mod.rs
@@ -0,0 +1,116 @@
+use std::error;
+use std::fmt;
+
+#[derive(Debug, Clone)]
+pub struct ResponseContent<T> {
+    pub status: reqwest::StatusCode,
+    pub content: String,
+    pub entity: Option<T>,
+}
+
+#[derive(Debug)]
+pub enum Error<T> {
+    Reqwest(reqwest::Error),
+    Serde(serde_json::Error),
+    Io(std::io::Error),
+    ResponseError(ResponseContent<T>),
+}
+
+impl <T> fmt::Display for Error<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let (module, e) = match self {
+            Error::Reqwest(e) => ("reqwest", e.to_string()),
+            Error::Serde(e) => ("serde", e.to_string()),
+            Error::Io(e) => ("IO", e.to_string()),
+            Error::ResponseError(e) => ("response", format!("status code {}", e.status)),
+        };
+        write!(f, "error in {}: {}", module, e)
+    }
+}
+
+impl <T: fmt::Debug> error::Error for Error<T> {
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+        Some(match self {
+            Error::Reqwest(e) => e,
+            Error::Serde(e) => e,
+            Error::Io(e) => e,
+            Error::ResponseError(_) => return None,
+        })
+    }
+}
+
+impl <T> From<reqwest::Error> for Error<T> {
+    fn from(e: reqwest::Error) -> Self {
+        Error::Reqwest(e)
+    }
+}
+
+impl <T> From<serde_json::Error> for Error<T> {
+    fn from(e: serde_json::Error) -> Self {
+        Error::Serde(e)
+    }
+}
+
+impl <T> From<std::io::Error> for Error<T> {
+    fn from(e: std::io::Error) -> Self {
+        Error::Io(e)
+    }
+}
+
+pub fn urlencode<T: AsRef<str>>(s: T) -> String {
+    ::url::form_urlencoded::byte_serialize(s.as_ref().as_bytes()).collect()
+}
+
+pub fn parse_deep_object(prefix: &str, value: &serde_json::Value) -> Vec<(String, String)> {
+    if let serde_json::Value::Object(object) = value {
+        let mut params = vec![];
+
+        for (key, value) in object {
+            match value {
+                serde_json::Value::Object(_) => params.append(&mut parse_deep_object(
+                    &format!("{}[{}]", prefix, key),
+                    value,
+                )),
+                serde_json::Value::Array(array) => {
+                    for (i, value) in array.iter().enumerate() {
+                        params.append(&mut parse_deep_object(
+                            &format!("{}[{}][{}]", prefix, key, i),
+                            value,
+                        ));
+                    }
+                },
+                serde_json::Value::String(s) => params.push((format!("{}[{}]", prefix, key), s.clone())),
+                _ => params.push((format!("{}[{}]", prefix, key), value.to_string())),
+            }
+        }
+
+        return params;
+    }
+
+    unimplemented!("Only objects are supported with style=deepObject")
+}
+
+/// Internal use only
+/// A content type supported by this client.
+#[allow(dead_code)]
+enum ContentType {
+    Json,
+    Text,
+    Unsupported(String)
+}
+
+impl From<&str> for ContentType {
+    fn from(content_type: &str) -> Self {
+        if content_type.starts_with("application") && content_type.contains("json") {
+            return Self::Json;
+        } else if content_type.starts_with("text/plain") {
+            return Self::Text;
+        } else {
+            return Self::Unsupported(content_type.to_string());
+        }
+    }
+}
+
+pub mod default_api;
+
+pub mod configuration;
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/lib.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/lib.rs
new file mode 100644
index 000000000000..e1520628d762
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/lib.rs
@@ -0,0 +1,11 @@
+#![allow(unused_imports)]
+#![allow(clippy::too_many_arguments)]
+
+extern crate serde_repr;
+extern crate serde;
+extern crate serde_json;
+extern crate url;
+extern crate reqwest;
+
+pub mod apis;
+pub mod models;
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/mod.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/mod.rs
new file mode 100644
index 000000000000..eaccca2eacd5
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/mod.rs
@@ -0,0 +1,6 @@
+pub mod sort_direction;
+pub use self::sort_direction::SortDirection;
+pub mod widget_kind;
+pub use self::widget_kind::WidgetKind;
+pub mod widget_summary;
+pub use self::widget_summary::WidgetSummary;
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/sort_direction.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/sort_direction.rs
new file mode 100644
index 000000000000..912c1ca38ea4
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/sort_direction.rs
@@ -0,0 +1,39 @@
+/*
+ * Nullable Enum Query Parameter Test
+ *
+ * Test spec for enum query parameters whose schema is not a bare $ref, as emitted by FastAPI and other 3.1 producers. The same operation is defined with and without a path parameter, because the two used to be generated differently.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ * Generated by: https://openapi-generator.tech
+ */
+
+use crate::models;
+use serde::{Deserialize, Serialize};
+
+/// SortDirection : Sort direction options
+/// Sort direction options
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize, Deserialize)]
+pub enum SortDirection {
+    #[serde(rename = "asc")]
+    Asc,
+    #[serde(rename = "desc")]
+    Desc,
+
+}
+
+impl std::fmt::Display for SortDirection {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Self::Asc => write!(f, "asc"),
+            Self::Desc => write!(f, "desc"),
+        }
+    }
+}
+
+impl Default for SortDirection {
+    fn default() -> SortDirection {
+        Self::Asc
+    }
+}
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/widget_kind.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/widget_kind.rs
new file mode 100644
index 000000000000..e43b5041cd95
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/widget_kind.rs
@@ -0,0 +1,39 @@
+/*
+ * Nullable Enum Query Parameter Test
+ *
+ * Test spec for enum query parameters whose schema is not a bare $ref, as emitted by FastAPI and other 3.1 producers. The same operation is defined with and without a path parameter, because the two used to be generated differently.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ * Generated by: https://openapi-generator.tech
+ */
+
+use crate::models;
+use serde::{Deserialize, Serialize};
+
+/// WidgetKind : Widget kind
+/// Widget kind
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize, Deserialize)]
+pub enum WidgetKind {
+    #[serde(rename = "basic")]
+    Basic,
+    #[serde(rename = "premium")]
+    Premium,
+
+}
+
+impl std::fmt::Display for WidgetKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Self::Basic => write!(f, "basic"),
+            Self::Premium => write!(f, "premium"),
+        }
+    }
+}
+
+impl Default for WidgetKind {
+    fn default() -> WidgetKind {
+        Self::Basic
+    }
+}
+
diff --git a/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/widget_summary.rs b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/widget_summary.rs
new file mode 100644
index 000000000000..fbd1f7cfa291
--- /dev/null
+++ b/samples/client/others/rust/reqwest/nullable-enum-query-params/src/models/widget_summary.rs
@@ -0,0 +1,30 @@
+/*
+ * Nullable Enum Query Parameter Test
+ *
+ * Test spec for enum query parameters whose schema is not a bare $ref, as emitted by FastAPI and other 3.1 producers. The same operation is defined with and without a path parameter, because the two used to be generated differently.
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ * Generated by: https://openapi-generator.tech
+ */
+
+use crate::models;
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, Default, Debug, PartialEq, Serialize, Deserialize)]
+pub struct WidgetSummary {
+    #[serde(rename = "kind")]
+    pub kind: models::WidgetKind,
+    #[serde(rename = "total")]
+    pub total: i32,
+}
+
+impl WidgetSummary {
+    pub fn new(kind: models::WidgetKind, total: i32) -> WidgetSummary {
+        WidgetSummary {
+            kind,
+            total,
+        }
+    }
+}
+