diff --git a/src/metadata/MetadataStorage.ts b/src/metadata/MetadataStorage.ts
index 18e4761eca..26a22be899 100644
--- a/src/metadata/MetadataStorage.ts
+++ b/src/metadata/MetadataStorage.ts
@@ -77,6 +77,8 @@ export class MetadataStorage {
         
         // get metadatas for inherited classes
         const inheritedMetadatas = this.validationMetadatas.filter(metadata => {
+              if (typeof metadata.target === "string")
+                return false;
             if (metadata.target === targetConstructor)
                 return false;
             if (metadata.target instanceof Function &&