diff --git a/tests/runtests.pl b/tests/runtests.pl
index 41f92629be..645db3939c 100755
--- a/tests/runtests.pl
+++ b/tests/runtests.pl
@@ -5379,7 +5379,7 @@ EOHELP
         $disabled{$1}=$1;
     }
     elsif($ARGV[0] =~ /^!(.+)/) {
-        $disabled_keywords{$1}=$1;
+        $disabled_keywords{lc($1)}=$1;
     }
     elsif($ARGV[0] =~ /^([-[{a-zA-Z].*)/) {
         $enabled_keywords{lc($1)}=$1;