diff --git a/vortex-datafusion/src/persistent/opener.rs b/vortex-datafusion/src/persistent/opener.rs
index 5986a06da49..95ae9f789e7 100644
--- a/vortex-datafusion/src/persistent/opener.rs
+++ b/vortex-datafusion/src/persistent/opener.rs
@@ -352,9 +352,7 @@ impl FileOpener for VortexOpener {
                 scan_builder = scan_builder.with_limit(limit);
             }
 
-            if let Some(concurrency) = scan_concurrency {
-                scan_builder = scan_builder.with_concurrency(concurrency);
-            }
+            scan_builder = scan_builder.with_concurrency(scan_concurrency.unwrap_or(4));
 
             let stream = scan_builder
                 .with_metrics_registry(metrics_registry)
diff --git a/vortex-scan/src/scan_builder.rs b/vortex-scan/src/scan_builder.rs
index 4c4548cc665..95ef40aea0a 100644
--- a/vortex-scan/src/scan_builder.rs
+++ b/vortex-scan/src/scan_builder.rs
@@ -349,10 +349,10 @@ impl<A: 'static + Send> Stream for LazyScanStream<A> {
                 LazyScanState::Builder(builder) => {
                     let builder = builder.take().vortex_expect("polled after completion");
                     let ordered = builder.ordered;
-                    let num_workers = std::thread::available_parallelism()
-                        .map(|n| n.get())
-                        .unwrap_or(1);
-                    let concurrency = builder.concurrency * num_workers;
+                    // let num_workers = std::thread::available_parallelism()
+                    //     .map(|n| n.get())
+                    //     .unwrap_or(1);
+                    let concurrency = builder.concurrency;
                     let handle = builder.session.handle();
                     let task = handle.spawn_blocking(move || {
                         builder.prepare().and_then(|scan| scan.execute(None))