diff --git a/plugins/apache/apache_memmory b/plugins/apache/apache_memmory
index 87a93a72..e8dd47e6 100755
--- a/plugins/apache/apache_memmory
+++ b/plugins/apache/apache_memmory
@@ -29,7 +29,7 @@ GPLv2
 
 =cut
 
-. $MUNIN_LIBDIR/plugins/plugin.sh
+. "$MUNIN_LIBDIR/plugins/plugin.sh"
 
 USR=${apuser:-www-data}
 PROCS=${binname:-apache2}