From 27ee14b2918ba5f5b63005480e56ef80bd126253 Mon Sep 17 00:00:00 2001
From: Wuzzy <almikes@aol.com>
Date: Tue, 21 Feb 2017 23:05:57 +0100
Subject: [PATCH] Fix sign being able to destroy block when building

---
 mods/ITEMS/signs/init.lua | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mods/ITEMS/signs/init.lua b/mods/ITEMS/signs/init.lua
index 30254c730..f80d2be90 100644
--- a/mods/ITEMS/signs/init.lua
+++ b/mods/ITEMS/signs/init.lua
@@ -211,6 +211,12 @@ minetest.register_node("signs:sign_wall", {
                      y = under.y - above.y,
                      z = under.z - above.z}
 
+	-- Only build when it's legal
+	local abovenodedef = minetest.registered_nodes[minetest.get_node(above)]
+	if not abovenodedef or abovenodedef.buildable_to == false then
+		return itemstack
+	end
+
         local wdir = minetest.dir_to_wallmounted(dir)
 
         local placer_pos = placer:getpos()