diff --git a/mods/mech/init.lua b/mods/mech/init.lua
index d0c9b3c..37628a0 100644
--- a/mods/mech/init.lua
+++ b/mods/mech/init.lua
@@ -630,9 +630,12 @@ minetest.register_node("mech:piston_base_extended", {
 				minetest.remove_node(npos)
 			end
 			node.name = "mech:piston_base_sticky"
-		else
+		elseif nnode.name == "mech:piston_top" then
 			minetest.remove_node(npos)
 			node.name = "mech:piston_base"
+		else
+			-- wall exploit otherwise
+			return
 		end
 		minetest.swap_node(pos, node)
 		minetest.sound_play("piston_untrigger", {pos = pos})