diff --git a/src/extensions/dnatco/confal-pyramids/property.ts b/src/extensions/dnatco/confal-pyramids/property.ts
index 00dcf95cc5787b736bca1ad6016d664c3bb188db..2fe28220ecc68e473206dbfb7157fd1f1c42745d 100644
--- a/src/extensions/dnatco/confal-pyramids/property.ts
+++ b/src/extensions/dnatco/confal-pyramids/property.ts
@@ -74,7 +74,7 @@ export namespace ConfalPyramids {
     }
 
     function hasNdbStructNtcCategories(model: Model): boolean {
-        if (!MmcifFormat.is(model.sourceData)) throw new Error('Data format must be mmCIF');
+        if (!MmcifFormat.is(model.sourceData)) return false;
         const names = (model.sourceData).data.frame.categoryNames;
         return names.includes('ndb_struct_ntc_step') && names.includes('ndb_struct_ntc_step_summary');
     }