diff --git a/lib/Doctrine/ORM/Query/Parser.php b/lib/Doctrine/ORM/Query/Parser.php
index 420083680..dfda6ee8a 100644
--- a/lib/Doctrine/ORM/Query/Parser.php
+++ b/lib/Doctrine/ORM/Query/Parser.php
@@ -1981,9 +1981,10 @@ class Parser
     }
 
     /**
-     * SimpleSelectExpression ::=
-     *      StateFieldPathExpression | IdentificationVariable |
-     *      ((AggregateExpression | "(" Subselect ")" | ScalarExpression) [["AS"] AliasResultVariable])
+     * SimpleSelectExpression ::= (
+     *      StateFieldPathExpression | IdentificationVariable | FunctionDeclaration |
+     *      AggregateExpression | "(" Subselect ")" | ScalarExpression
+     * ) [["AS"] AliasResultVariable]
      *
      * @return \Doctrine\ORM\Query\AST\SimpleSelectExpression
      */
@@ -2004,6 +2005,18 @@ class Parser
 
                         return new AST\SimpleSelectExpression($expression);
 
+                    case ($this->_isFunction()):
+                        // SUM(u.id) + COUNT(u.id)
+                        if ($this->_isMathOperator($this->_peekBeyondClosingParenthesis())) {
+                            return new AST\SimpleSelectExpression($this->ScalarExpression());
+                        }
+                        // COUNT(u.id)
+                        if ($this->_isAggregateFunction($this->_lexer->lookahead['type'])) {
+                            return new AST\SimpleSelectExpression($this->AggregateExpression());
+                        }
+                        // IDENTITY(u)
+                        return new AST\SimpleSelectExpression($this->FunctionDeclaration());
+
                     default:
                         // Do nothing
                 }
diff --git a/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php b/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
index a079e6574..7b1064c6e 100644
--- a/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
+++ b/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
@@ -1434,6 +1434,37 @@ class SelectSqlGenerationTest extends \Doctrine\Tests\OrmTestCase
         );
     }
 
+    /**
+     * @group DDC-1557
+     */
+    public function testSupportsSubSqlFunction()
+    {
+        $this->assertSqlGeneration(
+            'SELECT u1 FROM Doctrine\Tests\Models\CMS\CmsUser u1 WHERE u1.name IN ( SELECT TRIM(u2.name) FROM Doctrine\Tests\Models\CMS\CmsUser u2 )',
+            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 FROM cms_users c0_ WHERE c0_.name IN (SELECT TRIM(c1_.name) AS sclr4 FROM cms_users c1_)'
+        );
+        $this->assertSqlGeneration(
+            'SELECT u1 FROM Doctrine\Tests\Models\CMS\CmsUser u1 WHERE u1.name IN ( SELECT TRIM(u2.name) FROM Doctrine\Tests\Models\CMS\CmsUser u2  WHERE LOWER(u2.name) LIKE \'%fabio%\')',
+            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 FROM cms_users c0_ WHERE c0_.name IN (SELECT TRIM(c1_.name) AS sclr4 FROM cms_users c1_ WHERE LOWER(c1_.name) LIKE \'%fabio%\')'
+        );
+        $this->assertSqlGeneration(
+            'SELECT u1 FROM Doctrine\Tests\Models\CMS\CmsUser u1 WHERE u1.email IN ( SELECT TRIM(IDENTITY(u2.email)) FROM Doctrine\Tests\Models\CMS\CmsUser u2 )',
+            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 FROM cms_users c0_ WHERE c0_.email_id IN (SELECT TRIM(c1_.email_id) AS sclr4 FROM cms_users c1_)'
+        );
+        $this->assertSqlGeneration(
+            'SELECT u1 FROM Doctrine\Tests\Models\CMS\CmsUser u1 WHERE u1.email IN ( SELECT IDENTITY(u2.email) FROM Doctrine\Tests\Models\CMS\CmsUser u2 )',
+            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 FROM cms_users c0_ WHERE c0_.email_id IN (SELECT c1_.email_id AS sclr4 FROM cms_users c1_)'
+        );
+        $this->assertSqlGeneration(
+            'SELECT u1 FROM Doctrine\Tests\Models\CMS\CmsUser u1 WHERE COUNT(u1.id) = ( SELECT SUM(u2.id) FROM Doctrine\Tests\Models\CMS\CmsUser u2 )',
+            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 FROM cms_users c0_ WHERE COUNT(c0_.id) = (SELECT SUM(c1_.id) AS dctrn__1 FROM cms_users c1_)'
+        );
+        $this->assertSqlGeneration(
+            'SELECT u1 FROM Doctrine\Tests\Models\CMS\CmsUser u1 WHERE COUNT(u1.id) <= ( SELECT SUM(u2.id) + COUNT(u2.email) FROM Doctrine\Tests\Models\CMS\CmsUser u2 )',
+            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 FROM cms_users c0_ WHERE COUNT(c0_.id) <= (SELECT SUM(c1_.id) + COUNT(c1_.email_id) AS sclr4 FROM cms_users c1_)'
+        );
+    }
+
     public function testCustomTypeValueSql()
     {
         if (DBALType::hasType('negative_to_positive')) {