diff --git a/src/Infiltration/ui/Difficulty.ts b/src/Infiltration/ui/Difficulty.ts
index a0963abb8..5a64a896c 100644
--- a/src/Infiltration/ui/Difficulty.ts
+++ b/src/Infiltration/ui/Difficulty.ts
@@ -10,9 +10,9 @@ interface DifficultySettings {
 // I could use `any` to simply some of this but I also want to take advantage
 // of the type safety that typescript provides. I'm just not sure how in this
 // case.
-export function interpolate(settings: DifficultySettings, n: number, out: DifficultySetting): DifficultySetting {
+export function interpolate(settings: DifficultySettings, n: number, out: DifficultySetting): void {
   // interpolates between 2 difficulties.
-  function lerpD(a: DifficultySetting, b: DifficultySetting, t: number): DifficultySetting {
+  function lerpD(a: DifficultySetting, b: DifficultySetting, t: number): void {
     // interpolates between 2 numbers.
     function lerp(x: number, y: number, t: number): number {
       return (1 - t) * x + t * y;
@@ -20,7 +20,6 @@ export function interpolate(settings: DifficultySettings, n: number, out: Diffic
     for (const key of Object.keys(a)) {
       out[key] = lerp(a[key], b[key], t);
     }
-    return a;
   }
   if (n < 0) return lerpD(settings.Trivial, settings.Trivial, 0);
   if (n >= 0 && n < 1) return lerpD(settings.Trivial, settings.Normal, n);