diff --git a/cadence/contracts/FlowALPModels.cdc b/cadence/contracts/FlowALPModels.cdc
index cdd4a7b8..2a12257c 100644
--- a/cadence/contracts/FlowALPModels.cdc
+++ b/cadence/contracts/FlowALPModels.cdc
@@ -553,7 +553,7 @@ access(all) contract FlowALPModels {
             effectiveDebt: {Type: UFix128}
         ) {
             // Enforce single balance per token invariant: if a type appears in one map, it must not appear in the other.
-            for collateralType in effectiveCollateral.keys {
+            for collateralType in effectiveCollateral {
                 assert(effectiveDebt[collateralType] == nil, message: "cannot construct BalanceSheet: observed both credit and debit balance for \(collateralType.identifier)")
             }