diff --git a/builtin/common/misc_helpers.lua b/builtin/common/misc_helpers.lua
index b7bd4d6a7..be19e5b51 100644
--- a/builtin/common/misc_helpers.lua
+++ b/builtin/common/misc_helpers.lua
@@ -254,6 +254,7 @@ end
 
 
 function core.formspec_escape(text)
+	text = tostring(text)
 	if text ~= nil then
 		text = text:gsub("\\", "\\\\")
 		text = text:gsub("%]", "\\]")