diff --git a/classes/feeds.php b/classes/feeds.php
index d924eeb3e..d13c83a23 100644
--- a/classes/feeds.php
+++ b/classes/feeds.php
@@ -248,7 +248,7 @@ class Feeds extends Handler_Protected {
 		if (get_pref($this->link, 'COMBINED_DISPLAY_MODE')) {
 			$button_plugins = array();
 			foreach (explode(",", ARTICLE_BUTTON_PLUGINS) as $p) {
-				$pclass = trim("button_${p}");
+				$pclass = "button_" . trim($p);
 
 				if (class_exists($pclass)) {
 					$plugin = new $pclass($link);
diff --git a/include/functions.php b/include/functions.php
index eeed5650d..2994dd438 100644
--- a/include/functions.php
+++ b/include/functions.php
@@ -3434,7 +3434,7 @@
 				$button_plugins = explode(",", ARTICLE_BUTTON_PLUGINS);
 
 				foreach ($button_plugins as $p) {
-					$pclass = trim("button_${p}");
+					$pclass = "button_" . trim($p);
 
 					if (class_exists($pclass)) {
 						$plugin = new $pclass($link);