diff --git a/lib/Doctrine/ORM/Configuration.php b/lib/Doctrine/ORM/Configuration.php
index abb8a15d8..b6fa3a99e 100644
--- a/lib/Doctrine/ORM/Configuration.php
+++ b/lib/Doctrine/ORM/Configuration.php
@@ -339,6 +339,8 @@ class Configuration extends \Doctrine\DBAL\Configuration
      * Such a function can then be used in any DQL statement in any place where string
      * functions are allowed.
      *
+     * DQL function names are case-insensitive.
+     *
      * @param string $name
      * @param string $className
      */
@@ -355,6 +357,7 @@ class Configuration extends \Doctrine\DBAL\Configuration
      */
     public function getCustomStringFunction($name)
     {
+        $name = strtolower($name);
         return isset($this->_attributes['customStringFunctions'][$name]) ?
                 $this->_attributes['customStringFunctions'][$name] : null;
     }
@@ -371,7 +374,7 @@ class Configuration extends \Doctrine\DBAL\Configuration
      */
     public function setCustomStringFunctions(array $functions)
     {
-        $this->_attributes['customStringFunctions'] = $functions;
+        $this->_attributes['customStringFunctions'] = array_change_key_case($functions);
     }
 
     /**
@@ -379,6 +382,8 @@ class Configuration extends \Doctrine\DBAL\Configuration
      * Such a function can then be used in any DQL statement in any place where numeric
      * functions are allowed.
      *
+     * DQL function names are case-insensitive.
+     *
      * @param string $name
      * @param string $className
      */
@@ -395,6 +400,7 @@ class Configuration extends \Doctrine\DBAL\Configuration
      */
     public function getCustomNumericFunction($name)
     {
+        $name = strtolower($name);
         return isset($this->_attributes['customNumericFunctions'][$name]) ?
                 $this->_attributes['customNumericFunctions'][$name] : null;
     }
@@ -411,7 +417,7 @@ class Configuration extends \Doctrine\DBAL\Configuration
      */
     public function setCustomNumericFunctions(array $functions)
     {
-        $this->_attributes['customNumericFunctions'] = $functions;
+        $this->_attributes['customNumericFunctions'] = array_change_key_case($functions);
     }
 
     /**
@@ -419,6 +425,8 @@ class Configuration extends \Doctrine\DBAL\Configuration
      * Such a function can then be used in any DQL statement in any place where date/time
      * functions are allowed.
      *
+     * DQL function names are case-insensitive.
+     *
      * @param string $name
      * @param string $className
      */
@@ -435,6 +443,7 @@ class Configuration extends \Doctrine\DBAL\Configuration
      */
     public function getCustomDatetimeFunction($name)
     {
+        $name = strtolower($name);
         return isset($this->_attributes['customDatetimeFunctions'][$name]) ?
                 $this->_attributes['customDatetimeFunctions'][$name] : null;
     }
@@ -451,6 +460,6 @@ class Configuration extends \Doctrine\DBAL\Configuration
      */
     public function setCustomDatetimeFunctions(array $functions)
     {
-        $this->_attributes['customDatetimeFunctions'] = $functions;
+        $this->_attributes['customDatetimeFunctions'] = array_change_key_case($functions);
     }
 }
\ No newline at end of file
diff --git a/lib/Doctrine/ORM/Query/Parser.php b/lib/Doctrine/ORM/Query/Parser.php
index 645cb5ae0..960ae426d 100644
--- a/lib/Doctrine/ORM/Query/Parser.php
+++ b/lib/Doctrine/ORM/Query/Parser.php
@@ -2619,9 +2619,10 @@ class Parser
 
     public function CustomFunctionsReturningNumerics()
     {
-        $funcNameLower = strtolower($this->_lexer->lookahead['value']);
-        $funcClass = $this->_em->getConfiguration()->getCustomNumericFunction($funcNameLower);
-        $function = new $funcClass($funcNameLower);
+        $funcName = strtolower($this->_lexer->lookahead['value']);
+        // getCustomNumericFunction is case-insensitive
+        $funcClass = $this->_em->getConfiguration()->getCustomNumericFunction($funcName);
+        $function = new $funcClass($funcName);
         $function->parse($this);
 
         return $function;
@@ -2642,9 +2643,10 @@ class Parser
 
     public function CustomFunctionsReturningDatetime()
     {
-        $funcNameLower = strtolower($this->_lexer->lookahead['value']);
-        $funcClass = $this->_em->getConfiguration()->getCustomDatetimeFunction($funcNameLower);
-        $function = new $funcClass($funcNameLower);
+        $funcName = $this->_lexer->lookahead['value'];
+        // getCustomDatetimeFunction is case-insensitive
+        $funcClass = $this->_em->getConfiguration()->getCustomDatetimeFunction($funcName);
+        $function = new $funcClass($funcName);
         $function->parse($this);
 
         return $function;
@@ -2670,9 +2672,10 @@ class Parser
 
     public function CustomFunctionsReturningStrings()
     {
-        $funcNameLower = strtolower($this->_lexer->lookahead['value']);
-        $funcClass = $this->_em->getConfiguration()->getCustomStringFunction($funcNameLower);
-        $function = new $funcClass($funcNameLower);
+        $funcName = $this->_lexer->lookahead['value'];
+        // getCustomStringFunction is case-insensitive
+        $funcClass = $this->_em->getConfiguration()->getCustomStringFunction($funcName);
+        $function = new $funcClass($funcName);
         $function->parse($this);
 
         return $function;