diff --git a/game.cpp b/game.cpp
index 315d6a21..467d09dc 100644
--- a/game.cpp
+++ b/game.cpp
@@ -4278,6 +4278,15 @@ EX int pickDownDirection(cell *c, flagtype mf) {
   }
 
 EX vector<int> reverse_directions(cell *c, int dir) {
+  if(PURE) return reverse_directions(c->master, dir);
+  int d = c->degree();
+  if(d & 1)
+    return { gmod(dir + c->type/2, c->type), gmod(dir + (c->type+1)/2, c->type) };
+  else
+    return { gmod(dir + c->type/2, c->type) };
+  }
+
+EX vector<int> reverse_directions(heptagon *c, int dir) { 
   int d = c->degree();
   switch(geometry) {
     case gBinary3:
diff --git a/locations.cpp b/locations.cpp
index b54c07ca..4fcd634f 100644
--- a/locations.cpp
+++ b/locations.cpp
@@ -204,9 +204,6 @@ static const struct revstep_t { revstep_t() {}} revstep;
 
 extern int hrand(int);
 
-/** reverse directions are currently not implemented for heptagons */
-inline vector<int> reverse_directions(struct heptagon *c, int i) { throw "unimplemented"; }
-
 /** the walker structure is used for walking on surfaces defined via \ref connection_table. */
 template<class T> struct walker {
   /** where we are at */