diff --git a/mods/default/functions.lua b/mods/default/functions.lua
index bdc30158..87e7483b 100644
--- a/mods/default/functions.lua
+++ b/mods/default/functions.lua
@@ -297,7 +297,7 @@ function default.register_fence(name, def)
 		groups = {},
 	}
 	for k, v in pairs(default_fields) do
-		if not def[k] then
+		if def[k] == nil then
 			def[k] = v
 		end
 	end