diff --git a/autoflake.py b/autoflake.py
index 0766d05..ac33696 100755
--- a/autoflake.py
+++ b/autoflake.py
@@ -651,7 +651,9 @@ def fix_file(filename, args, standard_out):
 
     if original_source != filtered_source:
         if args.check:
-            standard_out.write('Unused imports/variables detected.')
+            standard_out.write(
+                '{filename}: Unused imports/variables detected'.format(
+                    filename=filename))
             sys.exit(1)
         if args.in_place:
             with open_with_encoding(filename, mode='w',