diff --git a/lbmpy_walberla/templates/Boundary.tmpl.h b/lbmpy_walberla/templates/Boundary.tmpl.h
index ecde6b57950ad4cb0880feabda85097829c5f348..6ae98b80750f2e0243170e40a06960c16adffaf8 100644
--- a/lbmpy_walberla/templates/Boundary.tmpl.h
+++ b/lbmpy_walberla/templates/Boundary.tmpl.h
@@ -139,6 +139,9 @@ public:
 
         auto * flagField = block->getData< FlagField_T > ( flagFieldID );
 
+        if( !(flagField->flagExists(boundaryFlagUID) && flagField->flagExists(domainFlagUID) ))
+            return;
+
         auto boundaryFlag = flagField->getFlag(boundaryFlagUID);
         auto domainFlag = flagField->getFlag(domainFlagUID);