diff --git a/contrib/check-code.py b/contrib/check-code.py
--- a/contrib/check-code.py
+++ b/contrib/check-code.py
@@ -467,6 +467,8 @@ def checkfile(f, logfunc=_defaultlogger.
             else:
                 p, msg = pat
                 ignore = None
+            if i >= nerrs:
+                msg = "warning: " + msg
 
             pos = 0
             n = 0
@@ -500,8 +502,7 @@ def checkfile(f, logfunc=_defaultlogger.
                         bl, bu, br = blamecache[n]
                         if bl == l:
                             bd = '%s@%s' % (bu, br)
-                if i >= nerrs:
-                    msg = "warning: " + msg
+
                 errors.append((f, lineno and n + 1, l, msg, bd))
                 result = False
 
diff --git a/tests/test-check-code.t b/tests/test-check-code.t
--- a/tests/test-check-code.t
+++ b/tests/test-check-code.t
@@ -185,12 +185,20 @@
   $ cat > warning.t <<EOF
   >   $ function warnonly {
   >   > }
+  >   $ diff -N aaa
+  >   $ function onwarn {}
   > EOF
   $ "$check_code" warning.t
   $ "$check_code" --warn warning.t
   warning.t:1:
    >   $ function warnonly {
    warning: don't use 'function', use old style
+  warning.t:3:
+   >   $ diff -N aaa
+   warning: don't use 'diff -N'
+  warning.t:4:
+   >   $ function onwarn {}
+   warning: don't use 'function', use old style
   [1]
   $ cat > raise-format.py <<EOF
   > raise SomeException, message