diff --git a/packages/aws-cdk-lib/aws-stepfunctions-tasks/lib/eventbridge/put-events.ts b/packages/aws-cdk-lib/aws-stepfunctions-tasks/lib/eventbridge/put-events.ts
index cb0f08bb9a311..dfb8694d801c6 100644
--- a/packages/aws-cdk-lib/aws-stepfunctions-tasks/lib/eventbridge/put-events.ts
+++ b/packages/aws-cdk-lib/aws-stepfunctions-tasks/lib/eventbridge/put-events.ts
@@ -132,17 +132,14 @@ export class EventBridgePutEvents extends sfn.TaskStateBase {
   }
 
   private renderEntries(): Object[] {
+    // we should have validated all entries in validateEntries()
     return this.props.entries.map(entry => {
-      if (entry.source?.startsWith('aws')) {
-        throw new Error('Event source cannot start with "aws."');
-      } else {
-        return {
-          Detail: entry.detail?.value,
-          DetailType: entry.detailType,
-          EventBusName: entry.eventBus?.eventBusArn,
-          Source: entry.source,
-        };
-      }
+      return {
+        Detail: entry.detail?.value,
+        DetailType: entry.detailType,
+        EventBusName: entry.eventBus?.eventBusArn,
+        Source: entry.source,
+      };
     });
   }
 
@@ -150,5 +147,8 @@ export class EventBridgePutEvents extends sfn.TaskStateBase {
     if (this.props.entries.length <= 0) {
       throw new Error('Value for property `entries` must be a non-empty array.');
     }
+    if (this.props.entries.some(e => e.source.startsWith('aws.'))) {
+      throw new Error('Event source cannot start with "aws."');
+    }
   }
 }
\ No newline at end of file
diff --git a/packages/aws-cdk-lib/aws-stepfunctions-tasks/test/eventbridge/put-events.test.ts b/packages/aws-cdk-lib/aws-stepfunctions-tasks/test/eventbridge/put-events.test.ts
index 67e98c798d32e..5a4a63221b504 100644
--- a/packages/aws-cdk-lib/aws-stepfunctions-tasks/test/eventbridge/put-events.test.ts
+++ b/packages/aws-cdk-lib/aws-stepfunctions-tasks/test/eventbridge/put-events.test.ts
@@ -161,6 +161,30 @@ describe('Put Events', () => {
     }).toThrowError('Unsupported service integration pattern');
   });
 
+  test('event source cannot start with "aws."', () => {
+    expect(() => {
+      new EventBridgePutEvents(stack, 'PutEvents', {
+        entries: [{
+          detail: sfn.TaskInput.fromText('MyDetail'),
+          detailType: 'MyDetailType',
+          source: 'aws.source',
+        }],
+      });
+    }).toThrow(/Event source cannot start with "aws."/);
+  });
+
+  test('event source can start with "aws" without trailing dot', () => {
+    expect(() => {
+      new EventBridgePutEvents(stack, 'PutEvents', {
+        entries: [{
+          detail: sfn.TaskInput.fromText('MyDetail'),
+          detailType: 'MyDetailType',
+          source: 'awssource',
+        }],
+      });
+    }).not.toThrow(/Event source cannot start with "aws."/);
+  });
+
   test('provided EventBus', () => {
     // GIVEN
     const eventBus = new events.EventBus(stack, 'EventBus');