diff --git a/ext/cIGraph_community.c b/ext/cIGraph_community.c
old mode 100644
new mode 100755
index 69568a5..854ce6b
--- a/ext/cIGraph_community.c
+++ b/ext/cIGraph_community.c
@@ -712,7 +712,7 @@ igraph_arpack_options_init(&arpack_opt);
 
  igraph_community_label_propagation(graph,
                                     &membership,
-                                    &weights_vec,
+                                    igraph_vector_size(&weights_vec) > 0 ? &weights_vec : NULL,
                                     NULL,
                                     NULL);