diff --git a/src/metadata.cc b/src/metadata.cc
index 6c1bc2ef..38802ef1 100755
--- a/src/metadata.cc
+++ b/src/metadata.cc
@@ -76,7 +76,9 @@ class MetadataWorker : public NanAsyncWorker {
       }
     }
     // Clean up
-    g_object_unref(image);
+    if (imageType != UNKNOWN) {
+      g_object_unref(image);
+    }
     vips_error_clear();
     vips_thread_shutdown();
   }