diff --git a/alberta/src/3d/memory_3d.c b/alberta/src/3d/memory_3d.c
index 32ddd2b3b3ecb16ad534a6d67fd1ba2a1941a2fd..05faaf96f6851c88ee9e44009a4949fcfad2e4ff 100644
--- a/alberta/src/3d/memory_3d.c
+++ b/alberta/src/3d/memory_3d.c
@@ -247,6 +247,7 @@ static void descend_tree_3d(LOGICAL_EL_3D *l_els,
 		"Oops, unknown vertex %d on element %d!\n", i, in_el);
   }
 
+  *n = -1;
   if((vertex[0] == in_vertex[0] && vertex[1] == in_vertex[1]) ||
      (vertex[0] == in_vertex[1] && vertex[1] == in_vertex[0])) {
     *n = 1;