diff --git a/src/php/lib/Grpc/BaseStub.php b/src/php/lib/Grpc/BaseStub.php
index aa4de349ea7..7b2627f516d 100755
--- a/src/php/lib/Grpc/BaseStub.php
+++ b/src/php/lib/Grpc/BaseStub.php
@@ -216,7 +216,7 @@ class BaseStub
      */
     public function _simpleRequest($method,
                                    $argument,
-                                   callable $deserialize,
+                                   $deserialize,
                                    $metadata = [],
                                    $options = [])
     {