diff --git a/lib/Doctrine/ORM/Query/Parser.php b/lib/Doctrine/ORM/Query/Parser.php
index 6a1e32acd..762cf67ce 100644
--- a/lib/Doctrine/ORM/Query/Parser.php
+++ b/lib/Doctrine/ORM/Query/Parser.php
@@ -3406,10 +3406,13 @@ class Parser
     public function CustomFunctionsReturningNumerics()
     {
         // getCustomNumericFunction is case-insensitive
-        $funcName  = strtolower($this->lexer->lookahead['value']);
-        $funcClass = $this->em->getConfiguration()->getCustomNumericFunction($funcName);
+        $functionName  = strtolower($this->lexer->lookahead['value']);
+        $functionClass = $this->em->getConfiguration()->getCustomNumericFunction($functionName);
+
+        $function = is_string($functionClass)
+            ? new $functionClass($functionName)
+            : $functionClass($functionName);
 
-        $function = new $funcClass($funcName);
         $function->parse($this);
 
         return $function;
@@ -3442,10 +3445,13 @@ class Parser
     public function CustomFunctionsReturningDatetime()
     {
         // getCustomDatetimeFunction is case-insensitive
-        $funcName  = $this->lexer->lookahead['value'];
-        $funcClass = $this->em->getConfiguration()->getCustomDatetimeFunction($funcName);
+        $functionName  = $this->lexer->lookahead['value'];
+        $functionClass = $this->em->getConfiguration()->getCustomDatetimeFunction($functionName);
+
+        $function = is_string($functionClass)
+            ? new $functionClass($functionName)
+            : $functionClass($functionName);
 
-        $function = new $funcClass($funcName);
         $function->parse($this);
 
         return $function;
@@ -3479,10 +3485,13 @@ class Parser
     public function CustomFunctionsReturningStrings()
     {
         // getCustomStringFunction is case-insensitive
-        $funcName  = $this->lexer->lookahead['value'];
-        $funcClass = $this->em->getConfiguration()->getCustomStringFunction($funcName);
+        $functionName  = $this->lexer->lookahead['value'];
+        $functionClass = $this->em->getConfiguration()->getCustomStringFunction($functionName);
+
+        $function = is_string($functionClass)
+            ? new $functionClass($functionName)
+            : $functionClass($functionName);
 
-        $function = new $funcClass($funcName);
         $function->parse($this);
 
         return $function;
diff --git a/tests/Doctrine/Tests/ORM/Functional/CustomFunctionsTest.php b/tests/Doctrine/Tests/ORM/Functional/CustomFunctionsTest.php
new file mode 100644
index 000000000..63c3e4ee9
--- /dev/null
+++ b/tests/Doctrine/Tests/ORM/Functional/CustomFunctionsTest.php
@@ -0,0 +1,72 @@
+<?php
+
+namespace Doctrine\Tests\ORM\Functional;
+
+use Doctrine\ORM\Query;
+use Doctrine\ORM\Query\AST\Functions\FunctionNode;
+use Doctrine\ORM\Query\AST\PathExpression;
+use Doctrine\ORM\Query\Lexer;
+use Doctrine\ORM\Query\Parser;
+use Doctrine\ORM\Query\SqlWalker;
+use Doctrine\Tests\Models\CMS\CmsUser;
+use Doctrine\Tests\OrmFunctionalTestCase;
+
+require_once __DIR__ . '/../../TestInit.php';
+
+class CustomFunctionsTest extends OrmFunctionalTestCase
+{
+    protected function setUp()
+    {
+        $this->useModelSet('cms');
+
+        parent::setUp();
+    }
+
+    public function testCustomFunctionDefinedWithCallback()
+    {
+        $user = new CmsUser();
+        $user->name = 'Bob';
+        $user->username = 'Dylan';
+        $this->_em->persist($user);
+        $this->_em->flush();
+
+        // Instead of defining the function with the class name, we use a callback
+        $this->_em->getConfiguration()->addCustomStringFunction('FOO', function($funcName) {
+            return new NoOp($funcName);
+        });
+        $this->_em->getConfiguration()->addCustomNumericFunction('BAR', function($funcName) {
+            return new NoOp($funcName);
+        });
+
+        $query = $this->_em->createQuery('SELECT u FROM Doctrine\Tests\Models\CMS\CmsUser u'
+            . ' WHERE FOO(u.name) = \'Bob\''
+            . ' AND BAR(1) = 1');
+
+        $users = $query->getResult();
+
+        $this->assertEquals(1, count($users));
+        $this->assertSame($user, $users[0]);
+    }
+}
+
+class NoOp extends FunctionNode
+{
+    /**
+     * @var PathExpression
+     */
+    private $field;
+
+    public function parse(Parser $parser)
+    {
+        $parser->match(Lexer::T_IDENTIFIER);
+        $parser->match(Lexer::T_OPEN_PARENTHESIS);
+        $this->field = $parser->ArithmeticPrimary();
+        $parser->match(Lexer::T_CLOSE_PARENTHESIS);
+    }
+
+    public function getSql(SqlWalker $sqlWalker)
+    {
+        return $this->field->dispatch($sqlWalker);
+    }
+}
+