diff --git a/src/runtime-three/runtime-scene-validation.ts b/src/runtime-three/runtime-scene-validation.ts
index ebd667a0..484a5735 100644
--- a/src/runtime-three/runtime-scene-validation.ts
+++ b/src/runtime-three/runtime-scene-validation.ts
@@ -1,5 +1,6 @@
 import type { LoadedModelAsset } from "../assets/gltf-model-import";
 import { getModelInstances } from "../assets/model-instances";
+import type { BoxBrush } from "../document/brushes";
 import type { SceneDocument } from "../document/scene-document";
 import {
   assertSceneDocumentIsValid,
@@ -8,6 +9,7 @@ import {
   type SceneDiagnostic
 } from "../document/scene-document-validation";
 import { getPrimaryPlayerStartEntity } from "../entities/entity-instances";
+import { validateBoxBrushGeometry } from "../geometry/box-brush-mesh";
 import { buildGeneratedModelCollider, ModelColliderGenerationError } from "../geometry/model-instance-collider-generation";
 
 export interface RuntimeSceneBuildValidationResult {
@@ -21,6 +23,12 @@ interface ValidateRuntimeSceneBuildOptions {
   loadedModelAssets?: Record<string, LoadedModelAsset>;
 }
 
+function validateBrushGeometry(brush: BoxBrush, path: string, diagnostics: SceneDiagnostic[]) {
+  for (const diagnostic of validateBoxBrushGeometry(brush)) {
+    diagnostics.push(createDiagnostic("error", diagnostic.code, diagnostic.message, `${path}.geometry`, "build"));
+  }
+}
+
 export function validateRuntimeSceneBuild(
   document: SceneDocument,
   options: ValidateRuntimeSceneBuildOptions
@@ -39,6 +47,10 @@ export function validateRuntimeSceneBuild(
     );
   }
 
+  for (const brush of Object.values(document.brushes)) {
+    validateBrushGeometry(brush, `brushes.${brush.id}`, diagnostics);
+  }
+
   for (const modelInstance of getModelInstances(document.modelInstances)) {
     const path = `modelInstances.${modelInstance.id}.collision.mode`;
     const asset = document.assets[modelInstance.assetId];