diff --git a/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddCorsPreflightIntegration.java b/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddCorsPreflightIntegration.java
index 72662bca34c..ad2eab0f11b 100644
--- a/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddCorsPreflightIntegration.java
+++ b/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddCorsPreflightIntegration.java
@@ -238,7 +238,7 @@ private static ObjectNode createPreflightIntegration(Map<CorsHeader, String> hea
             }
         }
 
-        // Ensure that the mock integration include the "type" = "mock" property.
-        return integration.build().toNode().expectObjectNode().withMember("type", "mock");
+        // Use createIntegration to fix the casing of the passThroughBehavior property.
+        return AddIntegrations.createIntegration(integration.build());
     }
 }
diff --git a/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddIntegrations.java b/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddIntegrations.java
index 5ca412912cb..e765f893eda 100644
--- a/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddIntegrations.java
+++ b/smithy-aws-apigateway-openapi/src/main/java/software/amazon/smithy/aws/apigateway/openapi/AddIntegrations.java
@@ -65,7 +65,13 @@ public OperationObject updateOperation(
                 });
     }
 
-    private ObjectNode createIntegration(
+    static ObjectNode createIntegration(MockIntegrationTrait integration) {
+        // The MockIntegrationTrait path doesn't use the context or shape,
+        // so it's safe to pass null here for those.
+        return createIntegration(null, null, integration);
+    }
+
+    private static ObjectNode createIntegration(
             Context<? extends Trait> context,
             OperationShape shape,
             Trait integration
diff --git a/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json b/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json
index 79422c2d9e6..e015324842f 100644
--- a/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json
+++ b/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-model.openapi.json
@@ -84,7 +84,7 @@
           "CORS"
         ],
         "x-amazon-apigateway-integration": {
-          "passThroughBehavior": "when_no_match",
+          "passthroughBehavior": "when_no_match",
           "contentHandling": "CONVERT_TO_TEXT",
           "requestTemplates": {
             "application/json": "{\"statusCode\":200}"
@@ -254,7 +254,7 @@
           "CORS"
         ],
         "x-amazon-apigateway-integration": {
-          "passThroughBehavior": "when_no_match",
+          "passthroughBehavior": "when_no_match",
           "contentHandling": "CONVERT_TO_TEXT",
           "requestTemplates": {
             "application/json": "{\"statusCode\":200}",
diff --git a/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-with-additional-headers.openapi.json b/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-with-additional-headers.openapi.json
index 5934c6992a8..7470b4afb9b 100644
--- a/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-with-additional-headers.openapi.json
+++ b/smithy-aws-apigateway-openapi/src/test/resources/software/amazon/smithy/aws/apigateway/openapi/cors-with-additional-headers.openapi.json
@@ -84,7 +84,7 @@
           "CORS"
         ],
         "x-amazon-apigateway-integration": {
-          "passThroughBehavior": "when_no_match",
+          "passthroughBehavior": "when_no_match",
           "contentHandling": "CONVERT_TO_TEXT",
           "requestTemplates": {
             "application/json": "{\"statusCode\":200}"
@@ -254,7 +254,7 @@
           "CORS"
         ],
         "x-amazon-apigateway-integration": {
-          "passThroughBehavior": "when_no_match",
+          "passthroughBehavior": "when_no_match",
           "contentHandling": "CONVERT_TO_TEXT",
           "requestTemplates": {
             "application/json": "{\"statusCode\":200}",