diff --git a/crystal.cpp b/crystal.cpp
index d8c80a32..deead13f 100644
--- a/crystal.cpp
+++ b/crystal.cpp
@@ -627,7 +627,7 @@ struct hrmap_crystal : hrmap_standard {
   map<int, transmatrix> adjs;
   
   transmatrix adj(heptagon *h, int d) override {
-    if(!crystal3()) return adj(h->c7, d);
+    if(!crystal3()) return hrmap_standard::adj(h, d);
     auto co = hcoords[h];
     int id = 0;
     for(int a=0; a<S7/2; a++) id = (2*id) + ((co[a]>>1) & 1);