diff --git a/src/stores/useModelStore.ts b/src/stores/useModelStore.ts
index b598904..3a15175 100644
--- a/src/stores/useModelStore.ts
+++ b/src/stores/useModelStore.ts
@@ -564,14 +564,15 @@ export const useModelStore = create<ModelStore>((set, get) => ({
       const distanceMM = distanceWorldMM / factor;
       // Convert world points to active model's local frame so they follow the model.
       const modelId = state.activeModelId ?? undefined;
-      const aLocal = (modelId && worldToModelLocal(modelId, a)) || a;
-      const bLocal = (modelId && worldToModelLocal(modelId, b)) || b;
+      const aConv = modelId ? worldToModelLocal(modelId, a) : null;
+      const bConv = modelId ? worldToModelLocal(modelId, b) : null;
+      const attached = !!(aConv && bConv);
       const measurement: Measurement = {
         id: `m_${Date.now()}`,
-        pointA: aLocal,
-        pointB: bLocal,
+        pointA: attached ? aConv! : a,
+        pointB: attached ? bConv! : b,
         distanceMM,
-        modelId: worldToModelLocal(modelId, a) ? modelId : undefined,
+        modelId: attached ? modelId : undefined,
       };
       return { measurePoints: [], measurements: [...state.measurements, measurement] };
     }