diff --git a/packages/aws-cdk-lib/core/lib/annotations.ts b/packages/aws-cdk-lib/core/lib/annotations.ts
index 19e83f0ec43af..2d5d75dab3ef0 100644
--- a/packages/aws-cdk-lib/core/lib/annotations.ts
+++ b/packages/aws-cdk-lib/core/lib/annotations.ts
@@ -143,7 +143,8 @@ export class Annotations {
   private addMessage(level: string, message: string) {
     const isNew = !this.scope.node.metadata.find((x) => x.data === message);
     if (isNew) {
-      this.scope.node.addMetadata(level, message, { stackTrace: this.stackTraces });
+      let normalizedMessage = typeof message === 'string' ? message : JSON.stringify(message);
+      this.scope.node.addMetadata(level, normalizedMessage, { stackTrace: this.stackTraces });
     }
   }
 }
@@ -259,4 +260,4 @@ function removeWarning(construct: IConstruct, id: string) {
 
 function ackTag(id: string) {
   return `[ack: ${id}]`;
-}
\ No newline at end of file
+}