diff --git a/tests/runtests.pl b/tests/runtests.pl
index ddda76f1c8..ee2f30873d 100755
--- a/tests/runtests.pl
+++ b/tests/runtests.pl
@@ -2206,7 +2206,7 @@ sub checksystem {
                 # given path to the "actual" windows path.
 
                 my @m = `mount`;
-                my $matchlen;
+                my $matchlen = 0;
                 my $bestmatch;
                 my $mount;