diff --git a/lib/Doctrine/ORM/Query/Parser.php b/lib/Doctrine/ORM/Query/Parser.php
index 4caee210c..a5e1fa1ab 100644
--- a/lib/Doctrine/ORM/Query/Parser.php
+++ b/lib/Doctrine/ORM/Query/Parser.php
@@ -1328,6 +1328,10 @@ class Parser
             $token = $this->_lexer->lookahead;
             $identVariable = $this->IdentificationVariable();
 
+            if (!isset($this->_queryComponents[$identVariable])) {
+                $this->semanticalError('Cannot group by undefined identification variable.');
+            }
+
             return $identVariable;
         }
 
diff --git a/lib/Doctrine/ORM/Query/QueryException.php b/lib/Doctrine/ORM/Query/QueryException.php
index f9dfd0823..aafe1e9d7 100644
--- a/lib/Doctrine/ORM/Query/QueryException.php
+++ b/lib/Doctrine/ORM/Query/QueryException.php
@@ -75,8 +75,7 @@ class QueryException extends \Doctrine\ORM\ORMException
     public static function invalidPathExpression($pathExpr)
     {
         return new self(
-            "Invalid PathExpression '" . $pathExpr->identificationVariable .
-            "." . implode('.', $pathExpr->parts) . "'."
+            "Invalid PathExpression '" . $pathExpr->identificationVariable . "." . $pathExpr->field . "'."
         );
     }
 
diff --git a/lib/Doctrine/ORM/Query/SqlWalker.php b/lib/Doctrine/ORM/Query/SqlWalker.php
index 5be2ee287..84a4f8308 100644
--- a/lib/Doctrine/ORM/Query/SqlWalker.php
+++ b/lib/Doctrine/ORM/Query/SqlWalker.php
@@ -1254,9 +1254,25 @@ class SqlWalker implements TreeWalker
      */
     public function walkGroupByClause($groupByClause)
     {
-        return ' GROUP BY ' . implode(
-            ', ', array_map(array($this, 'walkGroupByItem'), $groupByClause->groupByItems)
-        );
+        $sql = '';
+        foreach ($groupByClause->groupByItems AS $groupByItem) {
+            if (is_string($groupByItem)) {
+                foreach ($this->_queryComponents[$groupByItem]['metadata']->identifier AS $idField) {
+                    if ($sql != '') {
+                        $sql .= ', ';
+                    }
+                    $groupByItem = new AST\PathExpression(AST\PathExpression::TYPE_STATE_FIELD, $groupByItem, $idField);
+                    $groupByItem->type = AST\PathExpression::TYPE_STATE_FIELD;
+                    $sql .= $this->walkGroupByItem($groupByItem);
+                }
+            } else {
+                if ($sql != '') {
+                    $sql .= ', ';
+                }
+                $sql .= $this->walkGroupByItem($groupByItem);
+            }
+        }
+        return ' GROUP BY ' . $sql;
     }
 
     /**
diff --git a/tests/Doctrine/Tests/ORM/Query/LanguageRecognitionTest.php b/tests/Doctrine/Tests/ORM/Query/LanguageRecognitionTest.php
index fae0d7350..ff9d94b1f 100644
--- a/tests/Doctrine/Tests/ORM/Query/LanguageRecognitionTest.php
+++ b/tests/Doctrine/Tests/ORM/Query/LanguageRecognitionTest.php
@@ -496,6 +496,30 @@ class LanguageRecognitionTest extends \Doctrine\Tests\OrmTestCase
         $this->assertInvalidDQL('SELECT g FROM Doctrine\Tests\Models\CMS\CmsUser u JOIN u.groups g');
     }
 
+    /**
+     * @group DDC-1053
+     */
+    public function testGroupBy()
+    {
+        $this->assertValidDQL('SELECT g.id, count(u.id) FROM Doctrine\Tests\Models\CMS\CmsGroup g JOIN g.users u GROUP BY g.id');
+    }
+
+    /**
+     * @group DDC-1053
+     */
+    public function testGroupByIdentificationVariable()
+    {
+        $this->assertValidDQL('SELECT g, count(u.id) FROM Doctrine\Tests\Models\CMS\CmsGroup g JOIN g.users u GROUP BY g');
+    }
+
+    /**
+     * @group DDC-1053
+     */
+    public function testGroupByUnknownIdentificationVariable()
+    {
+        $this->assertInvalidDQL('SELECT g, count(u.id) FROM Doctrine\Tests\Models\CMS\CmsGroup g JOIN g.users u GROUP BY m');
+    }
+
     /**
      * @group DDC-117
      */
diff --git a/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php b/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
index 7b9cb4815..08fb9edb0 100644
--- a/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
+++ b/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
@@ -851,6 +851,28 @@ class SelectSqlGenerationTest extends \Doctrine\Tests\OrmTestCase
             'SELECT f0_.id AS id0, f0_.extension AS extension1, f0_.name AS name2 FROM "file" f0_ INNER JOIN Directory d1_ ON f0_.parentDirectory_id = d1_.id WHERE f0_.id = ?'
         );
     }
+
+    /**
+     * @group DDC-1053
+     */
+    public function testGroupBy()
+    {
+        $this->assertSqlGeneration(
+            'SELECT g.id, count(u.id) FROM Doctrine\Tests\Models\CMS\CmsGroup g JOIN g.users u GROUP BY g.id',
+            'SELECT c0_.id AS id0, count(c1_.id) AS sclr1 FROM cms_groups c0_ INNER JOIN cms_users_groups c2_ ON c0_.id = c2_.group_id INNER JOIN cms_users c1_ ON c1_.id = c2_.user_id GROUP BY c0_.id'
+        );
+    }
+
+    /**
+     * @group DDC-1053
+     */
+    public function testGroupByIdentificationVariable()
+    {
+        $this->assertSqlGeneration(
+            'SELECT g, count(u.id) FROM Doctrine\Tests\Models\CMS\CmsGroup g JOIN g.users u GROUP BY g',
+            'SELECT c0_.id AS id0, c0_.name AS name1, count(c1_.id) AS sclr2 FROM cms_groups c0_ INNER JOIN cms_users_groups c2_ ON c0_.id = c2_.group_id INNER JOIN cms_users c1_ ON c1_.id = c2_.user_id GROUP BY c0_.id'
+        );
+    }
 }