diff --git a/src/lua_maplib.c b/src/lua_maplib.c
index ece42b8d3dec950b8c6a904eb6370715963f2cd7..b7a779ed6de2c5e6b28aa3c629f5b5017d91b4e0 100644
--- a/src/lua_maplib.c
+++ b/src/lua_maplib.c
@@ -139,6 +139,7 @@ static const char *const side_opt[] = {
 	"toptexture",
 	"bottomtexture",
 	"midtexture",
+	"line",
 	"sector",
 	"special",
 	"repeatcnt",