diff --git a/src/core/operationstack.cpp b/src/core/operationstack.cpp
index 18ff942..32fc330 100644
--- a/src/core/operationstack.cpp
+++ b/src/core/operationstack.cpp
@@ -460,10 +460,13 @@ bool OperationStack::contains(const Partition* p) const
     foreach(Operation * o, operations()) {
         if (o->targets(*p))
             return true;
+
         CopyOperation* copyOp = dynamic_cast<CopyOperation*>(o);
-        const Partition* source = &copyOp->sourcePartition();
-        if (source == p)
-            return true;
+        if (copyOp) {
+            const Partition* source = &copyOp->sourcePartition();
+            if (source == p)
+                return true;
+        }
     }
 
     return false;