diff --git a/lib/Doctrine/ORM/Query/Parser.php b/lib/Doctrine/ORM/Query/Parser.php
index 762cf67ce..c64e731c6 100644
--- a/lib/Doctrine/ORM/Query/Parser.php
+++ b/lib/Doctrine/ORM/Query/Parser.php
@@ -3411,7 +3411,7 @@ class Parser
 
         $function = is_string($functionClass)
             ? new $functionClass($functionName)
-            : $functionClass($functionName);
+            : call_user_func($functionClass, $functionName);
 
         $function->parse($this);
 
@@ -3450,7 +3450,7 @@ class Parser
 
         $function = is_string($functionClass)
             ? new $functionClass($functionName)
-            : $functionClass($functionName);
+            : call_user_func($functionClass, $functionName);
 
         $function->parse($this);
 
@@ -3490,7 +3490,7 @@ class Parser
 
         $function = is_string($functionClass)
             ? new $functionClass($functionName)
-            : $functionClass($functionName);
+            : call_user_func($functionClass, $functionName);
 
         $function->parse($this);