diff --git a/tools/testing/ktest/ktest.pl b/tools/testing/ktest/ktest.pl
index b1bd8be3cf66..d752c4bd0d8b 100755
--- a/tools/testing/ktest/ktest.pl
+++ b/tools/testing/ktest/ktest.pl
@@ -2465,7 +2465,7 @@ sub check_buildlog {
     my $save_no_reboot = $no_reboot;
     $no_reboot = 1;
 
-    if (-f $warnings_file) {
+    if (defined($warnings_file) && -f $warnings_file) {
 	open(IN, $warnings_file) or
 	    dodie "Error opening $warnings_file";