diff --git a/packages/@aws-cdk/aws-stepfunctions-tasks/lib/aws-sdk/call-aws-service.ts b/packages/@aws-cdk/aws-stepfunctions-tasks/lib/aws-sdk/call-aws-service.ts
index dfd9ec1e4ba5c..f3987cc0677ae 100644
--- a/packages/@aws-cdk/aws-stepfunctions-tasks/lib/aws-sdk/call-aws-service.ts
+++ b/packages/@aws-cdk/aws-stepfunctions-tasks/lib/aws-sdk/call-aws-service.ts
@@ -67,6 +67,8 @@ export class CallAwsService extends sfn.TaskStateBase {
     this.taskPolicies = [
       new iam.PolicyStatement({
         resources: props.iamResources,
+        // The prefix and the action name are case insensitive
+        // https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_action.html
         actions: [props.iamAction ?? `${props.service}:${props.action}`],
       }),
     ];