diff --git a/src/runtime-three/first-person-navigation-controller.ts b/src/runtime-three/first-person-navigation-controller.ts
index c36910a5..093bb457 100644
--- a/src/runtime-three/first-person-navigation-controller.ts
+++ b/src/runtime-three/first-person-navigation-controller.ts
@@ -219,9 +219,12 @@ export class FirstPersonNavigationController implements NavigationController {
       return;
     }
 
-    const pointerLockResult = this.context.domElement.requestPointerLock();
+    const pointerLockCapableElement = this.context.domElement as HTMLCanvasElement & {
+      requestPointerLock(): void | Promise<void>;
+    };
+    const pointerLockResult = pointerLockCapableElement.requestPointerLock();
 
-    if (pointerLockResult !== undefined && "catch" in pointerLockResult) {
+    if (pointerLockResult instanceof Promise) {
       pointerLockResult.catch(() => {
         this.context?.setRuntimeMessage(
           "Pointer lock request was denied. Click again or use Orbit Visitor for non-locked navigation."
diff --git a/src/runtime-three/runtime-scene-build.ts b/src/runtime-three/runtime-scene-build.ts
index 3a02f921..6340bf38 100644
--- a/src/runtime-three/runtime-scene-build.ts
+++ b/src/runtime-three/runtime-scene-build.ts
@@ -66,6 +66,20 @@ function cloneVec3(vector: Vec3): Vec3 {
   };
 }
 
+function resolveRuntimeMaterial(document: SceneDocument, materialId: string | null): MaterialDef | null {
+  if (materialId === null) {
+    return null;
+  }
+
+  const material = document.materials[materialId];
+
+  if (material === undefined) {
+    throw new Error(`Runtime build could not resolve material ${materialId}.`);
+  }
+
+  return cloneMaterialDef(material);
+}
+
 function buildRuntimeBrush(brush: BoxBrush, document: SceneDocument): RuntimeBoxBrushInstance {
   return {
     id: brush.id,
@@ -75,32 +89,32 @@ function buildRuntimeBrush(brush: BoxBrush, document: SceneDocument): RuntimeBox
     faces: {
       posX: {
         materialId: brush.faces.posX.materialId,
-        material: brush.faces.posX.materialId === null ? null : cloneMaterialDef(document.materials[brush.faces.posX.materialId]),
+        material: resolveRuntimeMaterial(document, brush.faces.posX.materialId),
         uv: cloneFaceUvState(brush.faces.posX.uv)
       },
       negX: {
         materialId: brush.faces.negX.materialId,
-        material: brush.faces.negX.materialId === null ? null : cloneMaterialDef(document.materials[brush.faces.negX.materialId]),
+        material: resolveRuntimeMaterial(document, brush.faces.negX.materialId),
         uv: cloneFaceUvState(brush.faces.negX.uv)
       },
       posY: {
         materialId: brush.faces.posY.materialId,
-        material: brush.faces.posY.materialId === null ? null : cloneMaterialDef(document.materials[brush.faces.posY.materialId]),
+        material: resolveRuntimeMaterial(document, brush.faces.posY.materialId),
         uv: cloneFaceUvState(brush.faces.posY.uv)
       },
       negY: {
         materialId: brush.faces.negY.materialId,
-        material: brush.faces.negY.materialId === null ? null : cloneMaterialDef(document.materials[brush.faces.negY.materialId]),
+        material: resolveRuntimeMaterial(document, brush.faces.negY.materialId),
         uv: cloneFaceUvState(brush.faces.negY.uv)
       },
       posZ: {
         materialId: brush.faces.posZ.materialId,
-        material: brush.faces.posZ.materialId === null ? null : cloneMaterialDef(document.materials[brush.faces.posZ.materialId]),
+        material: resolveRuntimeMaterial(document, brush.faces.posZ.materialId),
         uv: cloneFaceUvState(brush.faces.posZ.uv)
       },
       negZ: {
         materialId: brush.faces.negZ.materialId,
-        material: brush.faces.negZ.materialId === null ? null : cloneMaterialDef(document.materials[brush.faces.negZ.materialId]),
+        material: resolveRuntimeMaterial(document, brush.faces.negZ.materialId),
         uv: cloneFaceUvState(brush.faces.negZ.uv)
       }
     }