diff --git a/src/runtime-three/first-person-navigation-controller.ts b/src/runtime-three/first-person-navigation-controller.ts
index 7298ca21..16e316a4 100644
--- a/src/runtime-three/first-person-navigation-controller.ts
+++ b/src/runtime-three/first-person-navigation-controller.ts
@@ -275,14 +275,14 @@ export class FirstPersonNavigationController implements NavigationController {
             inFog: false
           },
         probeGround: (feetPosition, shape, maxDistance) =>
-          this.context?.probePlayerGround(feetPosition, shape, maxDistance) ?? {
+          this.context?.probePlayerGround?.(feetPosition, shape, maxDistance) ?? {
             grounded: false,
             distance: null,
             normal: null,
             slopeDegrees: null
           },
         canOccupyShape: (feetPosition, shape) =>
-          this.context?.canOccupyPlayerShape(feetPosition, shape) ?? true
+          this.context?.canOccupyPlayerShape?.(feetPosition, shape) ?? true
       }
     );