diff --git a/src/ifcgeom/IfcGeomIteratorImplementation.h b/src/ifcgeom/IfcGeomIteratorImplementation.h
index cfa5d5d42a..e656d9e706 100644
--- a/src/ifcgeom/IfcGeomIteratorImplementation.h
+++ b/src/ifcgeom/IfcGeomIteratorImplementation.h
@@ -376,6 +376,8 @@ namespace IfcGeom {
 			if (num_threads_ != 1) {
 				collect();
 				process_concurrently();
+
+				return all_processed_elements_.size();
 			} else {
 				if (!create()) {
 					return false;