diff --git a/packages/@aws-cdk/core/lib/stack-synthesizers/default-synthesizer.ts b/packages/@aws-cdk/core/lib/stack-synthesizers/default-synthesizer.ts
index b4f9f29cf732a..a92d3b6fe04d0 100644
--- a/packages/@aws-cdk/core/lib/stack-synthesizers/default-synthesizer.ts
+++ b/packages/@aws-cdk/core/lib/stack-synthesizers/default-synthesizer.ts
@@ -291,7 +291,8 @@ export class DefaultStackSynthesizer extends StackSynthesizer {
     assertBound(this.bucketName);
     validateFileAssetSource(asset);
 
-    const objectKey = this.bucketPrefix + asset.sourceHash + (asset.packaging === FileAssetPackaging.ZIP_DIRECTORY ? '.zip' : '');
+    const extension = asset.fileName != undefined ? path.extname(asset.fileName) : '';
+    const objectKey = this.bucketPrefix + asset.sourceHash + (asset.packaging === FileAssetPackaging.ZIP_DIRECTORY ? '.zip' : extension);
 
     // Add to manifest
     this.files[asset.sourceHash] = {
diff --git a/packages/@aws-cdk/core/test/stack-synthesis/new-style-synthesis.test.ts b/packages/@aws-cdk/core/test/stack-synthesis/new-style-synthesis.test.ts
index 0131b7a4acc63..6780f07fbd879 100644
--- a/packages/@aws-cdk/core/test/stack-synthesis/new-style-synthesis.test.ts
+++ b/packages/@aws-cdk/core/test/stack-synthesis/new-style-synthesis.test.ts
@@ -52,7 +52,7 @@ nodeunitShim({
       destinations: {
         'current_account-current_region': {
           bucketName: 'cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}',
-          objectKey: templateHash,
+          objectKey: templateHash + '.json',
           assumeRoleArn: 'arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}',
         },
       },
@@ -111,7 +111,7 @@ nodeunitShim({
 
     // THEN - we have a fixed asset location with region placeholders
     test.equals(evalCFN(location.bucketName), 'cdk-hnb659fds-assets-the_account-the_region');
-    test.equals(evalCFN(location.s3Url), 'https://s3.the_region.domain.aws/cdk-hnb659fds-assets-the_account-the_region/abcdef');
+    test.equals(evalCFN(location.s3Url), 'https://s3.the_region.domain.aws/cdk-hnb659fds-assets-the_account-the_region/abcdef.js');
 
     // THEN - object key contains source hash somewhere
     test.ok(location.objectKey.indexOf('abcdef') > -1);
@@ -208,7 +208,7 @@ nodeunitShim({
 
     test.deepEqual(manifest.files?.['file-asset-hash']?.destinations?.['current_account-current_region'], {
       bucketName: 'file-asset-bucket',
-      objectKey: 'file-asset-hash',
+      objectKey: 'file-asset-hash.js',
       assumeRoleArn: 'file:role:arn',
       assumeRoleExternalId: 'file-external-id',
     });
@@ -256,7 +256,7 @@ nodeunitShim({
     // THEN
     test.deepEqual(manifest.files?.['file-asset-hash-with-prefix']?.destinations?.['current_account-current_region'], {
       bucketName: 'file-asset-bucket',
-      objectKey: '000000000000/file-asset-hash-with-prefix',
+      objectKey: '000000000000/file-asset-hash-with-prefix.js',
       assumeRoleArn: 'file:role:arn',
       assumeRoleExternalId: 'file-external-id',
     });