diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index dd2c262..8b80bac 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6390,7 +6390,7 @@
 		exit(0);
 	}
 
-	if (!$is_patch && $file !~ /cover-letter\.patch$/) {
+	if (!$is_patch && $filename !~ /cover-letter\.patch$/) {
 		ERROR("NOT_UNIFIED_DIFF",
 		      "Does not appear to be a unified-diff format patch\n");
 	}