diff --git a/src/mol-model/structure/structure/util/lookup3d.ts b/src/mol-model/structure/structure/util/lookup3d.ts
index beb7c150a40cc72668c78134543d78c80342d41a..2ea308e3ec11624d1528fa28d8d9f38e49f96fd0 100644
--- a/src/mol-model/structure/structure/util/lookup3d.ts
+++ b/src/mol-model/structure/structure/util/lookup3d.ts
@@ -84,7 +84,7 @@ export class StructureLookup3D implements Lookup3D<Element> {
     _boundary: { box: Box3D; sphere: Sphere3D; } | undefined = void 0;
 
     get boundary() {
-        if (this.boundary) return this._boundary!;
+        if (this._boundary) return this._boundary!;
         this._boundary = computeStructureBoundary(this.structure);
         return this._boundary!;
     }