diff --git a/src/Query/Mysql/IfNull.php b/src/Query/Mysql/IfNull.php
index 70dd852c..bbcdf61c 100644
--- a/src/Query/Mysql/IfNull.php
+++ b/src/Query/Mysql/IfNull.php
@@ -2,20 +2,28 @@
 
 namespace DoctrineExtensions\Query\Mysql;
 
+use Doctrine\ORM\Query\AST\ArithmeticExpression;
 use Doctrine\ORM\Query\AST\Functions\FunctionNode;
 use Doctrine\ORM\Query\Parser;
 use Doctrine\ORM\Query\SqlWalker;
 use Doctrine\ORM\Query\TokenType;
 
 /**
- * "IFNULL" "(" ArithmeticExpression "," ArithmeticExpression ")"
+ * IfNullFunction ::= "IFNULL" "(" ArithmeticExpression "," ArithmeticExpression ")"
+ *
+ * @link https://dev.mysql.com/doc/refman/en/flow-control-functions.html#function_ifnull
  *
  * @author Andrew Mackrodt <andrew@ajmm.org>
+ *
+ * @example SELECT IFNULL(null, 2)
+ * @example SELECT IFNULL(foo.bar, 1) FROM entity
  */
 class IfNull extends FunctionNode
 {
+    /** @var ArithmeticExpression */
     private $expr1;
 
+    /** @var ArithmeticExpression */
     private $expr2;
 
     public function parse(Parser $parser): void