diff --git a/xs/src/admesh/shared.c b/xs/src/admesh/shared.c
index 62a1d95c..59fbbb21 100644
--- a/xs/src/admesh/shared.c
+++ b/xs/src/admesh/shared.c
@@ -26,10 +26,14 @@
 void
 stl_invalidate_shared_vertices(stl_file *stl)
 {
-    if (stl->v_indices != NULL)
+    if (stl->v_indices != NULL) {
         free(stl->v_indices);
-    if (stl->v_shared != NULL)
+        stl->v_indices = NULL;
+    }
+    if (stl->v_shared != NULL) {
         free(stl->v_shared);
+        stl->v_shared = NULL;
+    }
 }
 
 void
diff --git a/xs/xsp/TriangleMesh.xsp b/xs/xsp/TriangleMesh.xsp
index 58fc9bb9..7f47df61 100644
--- a/xs/xsp/TriangleMesh.xsp
+++ b/xs/xsp/TriangleMesh.xsp
@@ -37,7 +37,7 @@ TriangleMesh::stats()
 SV*
 TriangleMesh::vertices()
     CODE:
-        if (THIS->stl.stats.shared_vertices == 0)
+        if (THIS->stl.v_shared == NULL)
             stl_generate_shared_vertices(&(THIS->stl));
         
         // vertices
@@ -59,7 +59,7 @@ TriangleMesh::vertices()
 SV*
 TriangleMesh::facets()
     CODE:
-        if (THIS->stl.stats.shared_vertices == 0)
+        if (THIS->stl.v_shared == NULL)
             stl_generate_shared_vertices(&(THIS->stl));
         
         // facets