diff --git a/lualib/sprotoparser.lua b/lualib/sprotoparser.lua
index cfa25afa..6b3741e9 100644
--- a/lualib/sprotoparser.lua
+++ b/lualib/sprotoparser.lua
@@ -348,6 +348,7 @@ local function packtype(name, t, alltypes)
 		else
 			tmp.type = nil
 		end
+		tmp.map = nil
 		if f.key then
 			assert(f.array)
 			if f.key == "" then