minor syntax
diff --git a/test/test_flac.sh b/test/test_flac.sh
index 4876f55..70a1684 100755
--- a/test/test_flac.sh
+++ b/test/test_flac.sh
@@ -31,7 +31,7 @@
 
 run_flac ()
 {
-	if [ "$FLAC__VALGRIND" = yes ] ; then
+	if [ x"$FLAC__VALGRIND" = xyes ] ; then
 		valgrind --leak-check=yes --show-reachable=yes --num-callers=100 --logfile-fd=4 flac $* 4>>test_flac.valgrind.log
 	else
 		flac $*