diff --git a/src/jsutils/memoize3.js b/src/jsutils/memoize3.js
index c8b1938a63..925b72d570 100644
--- a/src/jsutils/memoize3.js
+++ b/src/jsutils/memoize3.js
@@ -5,7 +5,7 @@ export function memoize3<
   A1: { ... } | $ReadOnlyArray<mixed>,
   A2: { ... } | $ReadOnlyArray<mixed>,
   A3: { ... } | $ReadOnlyArray<mixed>,
-  R: mixed,
+  R,
 >(fn: (A1, A2, A3) => R): (A1, A2, A3) => R {
   let cache0;