diff --git a/AMDiS/src/Operator.cc b/AMDiS/src/Operator.cc
index 946b8d4b91838059163597f9263104a3c012f0a1..f0d5ca7cf749b9acf19ee144aab416c993b326cd 100644
--- a/AMDiS/src/Operator.cc
+++ b/AMDiS/src/Operator.cc
@@ -168,7 +168,8 @@ namespace AMDiS {
 
   void Operator::finishAssembling()
   {
-    assembler->finishAssembling();
+    if (assembler)
+      assembler->finishAssembling();
   }