diff --git a/_tags b/_tags
index 3f37eb9..ba3d954 100644
--- a/_tags
+++ b/_tags
@@ -48,7 +48,7 @@
 
 <src_marshal_defs/marshal_defs.{d.byte,byte,native,p.native}> : package(lem), package(base64)
 
-<src_top/main.{d.byte,byte,native,p.native}> : package(unix), package(str), package(lem), package(linksem), package(base64)
+<src_top/main.{d.byte,byte,native,p.native}> : thread, package(unix), package(str), package(lem), package(linksem), package(base64)
 # the Makefile also adds package(lambda-term) when building text (and not headless)
 
 <src_top/webppc.{d.byte,byte}> : package(unix), package(js_of_ocaml), package(lem), package(linksem), package(base64)