diff --git a/stubs/Reflection.phpstub b/stubs/Reflection.phpstub
index 166e2a677..478dfdf80 100644
--- a/stubs/Reflection.phpstub
+++ b/stubs/Reflection.phpstub
@@ -432,7 +432,11 @@ abstract class ReflectionFunctionAbstract implements Reflector
 
 class ReflectionFunction extends ReflectionFunctionAbstract
 {
-    /** @psalm-pure */
+    /**
+     * @param callable-string|Closure $function
+     *
+     * @psalm-pure
+     */
     public function __construct(callable $function) {}
 
     /**