diff --git a/src/pmsearch b/src/pmsearch
index 16f0c38..08ef53b 100755
--- a/src/pmsearch
+++ b/src/pmsearch
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-if [ ${1} = "" ]; then
+if [ "${1}" == "" ]; then
 	printf "usage: pmsearch FILTER\n"
 	exit 1
 fi