diff --git a/gio/gunixmounts.c b/gio/gunixmounts.c
index 931bbb9e9..c0af1dc87 100644
--- a/gio/gunixmounts.c
+++ b/gio/gunixmounts.c
@@ -1023,6 +1023,7 @@ _g_get_unix_mount_points (void)
   GList *return_list;
 #ifdef HAVE_SYS_SYSCTL_H
   int usermnt = 0;
+  size_t len = sizeof(usermnt);
   struct stat sb;
 #endif