diff --git a/net/l2tp/src/etc/inc/plugins.inc.d/if_l2tp.inc b/net/l2tp/src/etc/inc/plugins.inc.d/if_l2tp.inc
index baa71d131..08fec9c88 100644
--- a/net/l2tp/src/etc/inc/plugins.inc.d/if_l2tp.inc
+++ b/net/l2tp/src/etc/inc/plugins.inc.d/if_l2tp.inc
@@ -32,7 +32,7 @@
 
 /* BEGIN remove this in 17.1: provide compat for newer plugin on stock 16.7 */
 require_once 'util.inc';
-if (!function_exists(url_safe)) {
+if (!function_exists('url_safe')) {
     function url_safe($format, $args = array())
     {
         if (!is_array($args)) {
diff --git a/net/pppoe/src/etc/inc/plugins.inc.d/if_pppoe.inc b/net/pppoe/src/etc/inc/plugins.inc.d/if_pppoe.inc
index fad2888ea..f78f313d8 100644
--- a/net/pppoe/src/etc/inc/plugins.inc.d/if_pppoe.inc
+++ b/net/pppoe/src/etc/inc/plugins.inc.d/if_pppoe.inc
@@ -32,7 +32,7 @@
 
 /* BEGIN remove this in 17.1: provide compat for newer plugin on stock 16.7 */
 require_once 'util.inc';
-if (!function_exists(url_safe)) {
+if (!function_exists('url_safe')) {
     function url_safe($format, $args = array())
     {
         if (!is_array($args)) {
diff --git a/net/pptp/src/etc/inc/plugins.inc.d/if_pptp.inc b/net/pptp/src/etc/inc/plugins.inc.d/if_pptp.inc
index ee86a0f0f..535908b78 100644
--- a/net/pptp/src/etc/inc/plugins.inc.d/if_pptp.inc
+++ b/net/pptp/src/etc/inc/plugins.inc.d/if_pptp.inc
@@ -32,7 +32,7 @@
 
 /* BEGIN remove this in 17.1: provide compat for newer plugin on stock 16.7 */
 require_once 'util.inc';
-if (!function_exists(url_safe)) {
+if (!function_exists('url_safe')) {
     function url_safe($format, $args = array())
     {
         if (!is_array($args)) {