diff --git a/RoutingAlgorithms/ShortestPathRouting.h b/RoutingAlgorithms/ShortestPathRouting.h
index 6738155a6..982b7b13d 100644
--- a/RoutingAlgorithms/ShortestPathRouting.h
+++ b/RoutingAlgorithms/ShortestPathRouting.h
@@ -225,8 +225,8 @@ public:
             std::vector<NodeID> temporary_packed_leg1;
             std::vector<NodeID> temporary_packed_leg2;
 
-            BOOST_ASSERT( current_leg < packed_legs1.size() );
-            BOOST_ASSERT( current_leg < packed_legs2.size() );
+            BOOST_ASSERT( (unsigned)current_leg < packed_legs1.size() );
+            BOOST_ASSERT( (unsigned)current_leg < packed_legs2.size() );
 
             if(INT_MAX != local_upper_bound1) {
                 super::RetrievePackedPathFromHeap(