diff --git a/sapfor/experts/Sapfor_2017/_src/GraphLoop/graph_loops.h b/sapfor/experts/Sapfor_2017/_src/GraphLoop/graph_loops.h
index 50878b7..d483eda 100644
--- a/sapfor/experts/Sapfor_2017/_src/GraphLoop/graph_loops.h
+++ b/sapfor/experts/Sapfor_2017/_src/GraphLoop/graph_loops.h
@@ -211,7 +211,7 @@ public:
         }
 
         ParallelDirective *parDirective = baseDirs[0];
-        for (int z = 1; z < baseDirs.size(); ++z)
+        for (int z = 1; z < baseDirs.size() && baseDirs[z]; ++z)
         {
             ParallelDirective *old = parDirective;
             parDirective = *parDirective + *baseDirs[z];