diff --git a/cell.cpp b/cell.cpp
index c88b182e..89fc9f7d 100644
--- a/cell.cpp
+++ b/cell.cpp
@@ -880,6 +880,7 @@ int heptdistance(heptagon *h1, heptagon *h2) {
   #if CAP_CRYSTAL
   if(geometry == gCrystal) return crystal::space_distance(h1->c7, h2->c7);
   #endif
+  if(sol) return solv::approx_distance(h1, h2);
   while(true) {
     if(h1 == h2) return d;
     for(int i=0; i<S7; i++) if(h1->move(i) == h2) return d + 1;
diff --git a/sol.cpp b/sol.cpp
index 1d90cced..b756f1f4 100644
--- a/sol.cpp
+++ b/sol.cpp
@@ -393,7 +393,16 @@ namespace solv {
 
     return rspintox(inverse(back_Position) * back_goal);
     }
-
+  
+  int approx_distance(heptagon *h1, heptagon *h2) {
+    auto m = (hrmap_sol*) currentmap;
+    dynamicval<eGeometry> g(geometry, gBinary4); 
+    dynamicval<hrmap*> cm(currentmap, m->binary_map);
+    int d1 = binary::celldistance3_approx(m->coords[h1].first, m->coords[h2].first);
+    int d2 = binary::celldistance3_approx(m->coords[h1].second, m->coords[h2].second);
+    return d1 + d2 - abs(h1->distance - h2->distance);
+    }
+  
   string solshader = 
     "uniform mediump sampler3D tInvExpTable;"    
     "uniform mediump float PRECX, PRECY, PRECZ;"