diff --git a/js/game.js b/js/game.js
index 2e7b4c9..d10651c 100644
--- a/js/game.js
+++ b/js/game.js
@@ -1217,29 +1217,33 @@ export class Level extends LevelInterface {
 
     _do_post_actor_phase() {
         if (this.pending_green_toggle) {
-            // Swap green floors and walls
-            // TODO could probably make this more compact for undo purposes
-            for (let cell of this.linear_cells) {
-                let terrain = cell.get_terrain();
-                if (terrain.type.name === 'green_floor') {
-                    this.transmute_tile(terrain, 'green_wall');
-                }
-                else if (terrain.type.name === 'green_wall') {
-                    this.transmute_tile(terrain, 'green_floor');
-                }
-
-                let item = cell.get_item();
-                if (item && item.type.name === 'green_chip') {
-                    this.transmute_tile(item, 'green_bomb');
-                }
-                else if (item && item.type.name === 'green_bomb') {
-                    this.transmute_tile(item, 'green_chip');
-                }
-            }
+            // Swap green objects
+            this.__toggle_green_tiles();
+            this._push_pending_undo(() => {
+                this.__toggle_green_tiles();
+            });
             this.pending_green_toggle = false;
         }
     }
 
+    __toggle_green_tiles() {
+        // This is NOT undo-safe; it's undone by calling it again!
+        // Assumes:
+        // 1. Green tile types come in pairs, which toggle into one another
+        // 2. A pair of green tile types appear on the same layer
+        for (let cell of this.linear_cells) {
+            let terrain = cell.get_terrain();
+            if (terrain.type.green_toggle_counterpart) {
+                terrain.type = TILE_TYPES[terrain.type.green_toggle_counterpart];
+            }
+
+            let item = cell.get_item();
+            if (item && item.type.green_toggle_counterpart) {
+                item.type = TILE_TYPES[item.type.green_toggle_counterpart];
+            }
+        }
+    }
+
     _do_cleanup_phase() {
         // Lynx compat: Any blue tank that still has the reversal flag set here, but is in motion,
         // should ignore it.  Unfortunately this has to be done as its own pass (as it is in Lynx!)
diff --git a/js/tiletypes.js b/js/tiletypes.js
index a54c363..caf4207 100644
--- a/js/tiletypes.js
+++ b/js/tiletypes.js
@@ -1317,6 +1317,7 @@ const TILE_TYPES = {
     },
     green_floor: {
         layer: LAYERS.terrain,
+        green_toggle_counterpart: 'green_wall',
         blocks(me, level, other) {
             // Toggle walls don't toggle until the end of the frame, but the collision takes into
             // account whether a toggle is coming
@@ -1333,6 +1334,7 @@ const TILE_TYPES = {
     },
     green_wall: {
         layer: LAYERS.terrain,
+        green_toggle_counterpart: 'green_floor',
         blocks(me, level, other) {
             // Same as above
             return (
@@ -1350,6 +1352,7 @@ const TILE_TYPES = {
         layer: LAYERS.item,
         is_chip: true,
         is_required_chip: true,
+        green_toggle_counterpart: 'green_bomb',
         blocks_collision: COLLISION.block_cc1 | COLLISION.monster_typical,
         item_priority: PICKUP_PRIORITIES.real_player,
         on_pickup(me, level, other) {
@@ -1361,6 +1364,7 @@ const TILE_TYPES = {
     green_bomb: {
         layer: LAYERS.item,
         is_required_chip: true,
+        green_toggle_counterpart: 'green_chip',
         on_arrive(me, level, other) {
             // Unlike regular bombs, these only seem to respond to being stepped on, not stood on
             level.remove_tile(me);