diff --git a/build/gen_stub.php b/build/gen_stub.php
index b3f3fcfba63..a83c6c13bf8 100755
--- a/build/gen_stub.php
+++ b/build/gen_stub.php
@@ -999,7 +999,7 @@ class PropertyName implements VariableLikeName {
         $this->property = $property;
     }
 
-    public function __toString()
+    public function __toString(): string
     {
         return $this->class->toString() . "::$" . $this->property;
     }
@@ -1690,7 +1690,7 @@ class EvaluatedValue
                     return null;
                 }
 
-                throw new Exception("Constant " . $originatingConstName->__toString() . " cannot be found");
+                throw new Exception("Constant " . $constName . " cannot be found");
             }
         );