diff --git a/celldrawer.cpp b/celldrawer.cpp
index f24b3104..ef48a0a3 100644
--- a/celldrawer.cpp
+++ b/celldrawer.cpp
@@ -1528,7 +1528,7 @@ void celldrawer::draw_features_and_walls_3d() {
     for(int a=0; a<c->type; a++) {
       bool b = true;
       if(c->move(a) && (among(pmodel, mdPerspective, mdGeodesic) || gmatrix0.count(c->move(a))))
-        b = !isWall3(c->move(a), dummy);
+        b = (patterns::innerwalls && (tC0(V)[2] < tC0(V * currentmap->adj(c, a))[2])) || !isWall3(c->move(a), dummy);
       if(b) {
         if(pmodel == mdPerspective && !sphere && !quotient && !penrose && !nonisotropic && !hybri && !experimental && !nih) {
           if(a < 4 && among(geometry, gHoroTris, gBinary3) && celldistAlt(c) >= celldistAlt(centerover)) continue;
diff --git a/pattern2.cpp b/pattern2.cpp
index 6770f242..45eb772c 100644
--- a/pattern2.cpp
+++ b/pattern2.cpp
@@ -1494,6 +1494,7 @@ EX namespace patterns {
   EX bool displaycodes;
   EX char whichShape = 0;
   EX char whichCanvas = 0;
+  EX bool innerwalls;
   
   int sevenval(cell *c) {
     if(!euclid) return 0;
@@ -1789,6 +1790,7 @@ EX namespace patterns {
 
     dialog::addBreak(100);
 
+    dialog::addBoolItem_action(XLAT("display the inner walls"), innerwalls, '5');
     dialog::addBoolItem(XLAT("display only hexagons"), (whichShape == '6'), '6');
     dialog::addBoolItem(XLAT("display only heptagons"), (whichShape == '7'), '7');
     dialog::addBoolItem(XLAT("display the triheptagonal grid"), (whichShape == '8'), '8');
@@ -2857,7 +2859,14 @@ int read_pattern_args() {
     patterns::whichCanvas = 'f';
     shift(); patterns::color_formula = args();
     }
-
+  else if(argis("-innerwall")) {
+    PHASEFROM(2);
+    patterns::innerwalls = true;
+    }
+  else if(argis("-noinnerwall")) {
+    PHASEFROM(2);
+    patterns::innerwalls = false;
+    }
   else if(argis("-d:line")) 
     launch_dialog(linepatterns::showMenu);