diff --git a/lib/checksrc.pl b/lib/checksrc.pl
index 965f0bab1..b2cfa8355 100755
--- a/lib/checksrc.pl
+++ b/lib/checksrc.pl
@@ -176,7 +176,7 @@ sub checkwarn {
 
 $file = shift @ARGV;
 
-while(1) {
+while(defined $file) {
 
     if($file =~ /-D(.*)/) {
         $dir = $1;