diff --git a/packages/catalog-model/src/kinds/ApiEntityV1alpha1.test.ts b/packages/catalog-model/src/kinds/ApiEntityV1alpha1.test.ts
index a4d7d904cd..249243bed3 100644
--- a/packages/catalog-model/src/kinds/ApiEntityV1alpha1.test.ts
+++ b/packages/catalog-model/src/kinds/ApiEntityV1alpha1.test.ts
@@ -168,4 +168,16 @@ components:
     (entity as any).spec.system = '';
     await expect(validator.check(entity)).rejects.toThrow(/system/);
   });
+
+  it('rejects additional properties', async () => {
+    (entity as any).annotations = 'Test';
+    await expect(validator.check(entity)).rejects.toThrow(
+      /additional properties/,
+    );
+  });
+
+  it('rejects with useful error message', async () => {
+    (entity as any).annotations = 'Test';
+    await expect(validator.check(entity)).rejects.toThrow(/annotations/);
+  });
 });
diff --git a/packages/catalog-model/src/kinds/util.ts b/packages/catalog-model/src/kinds/util.ts
index 4002f2806c..1e9e7b7521 100644
--- a/packages/catalog-model/src/kinds/util.ts
+++ b/packages/catalog-model/src/kinds/util.ts
@@ -66,7 +66,13 @@ export function ajvCompiledJsonSchemaValidator(
       }
 
       throw new TypeError(
-        `Malformed ${kind}, ${error.dataPath || '<root>'} ${error.message}`,
+        `Malformed ${kind}, ${error.dataPath || '<root>'} ${error.message}${
+          error.params
+            ? ` - ${Object.entries(error.params)
+                .map(([key, val]) => `${key}: ${val}`)
+                .join(', ')}`
+            : ''
+        }`,
       );
     },
   };