diff --git a/tools/wrc/wrc.c b/tools/wrc/wrc.c
index c3dfa418571..2448fff11eb 100644
--- a/tools/wrc/wrc.c
+++ b/tools/wrc/wrc.c
@@ -302,7 +302,7 @@ static void init_argv0_dir( const char *argv0 )
     static int pathname[] = { CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1 };
     size_t path_size = PATH_MAX;
     char *path = xmalloc( path_size );
-    if (!sysctl( pathname, sizeof(pathname)/sizeof(pathname[0]), path, &path_size, NULL, 0 ))
+    if (!sysctl( pathname, ARRAY_SIZE(pathname), path, &path_size, NULL, 0 ))
         dir = realpath( path, NULL );
     free( path );
 #else