diff --git a/lakefile.lean b/lakefile.lean
index e0446c68..0fed3d47 100644
--- a/lakefile.lean
+++ b/lakefile.lean
@@ -12,3 +12,6 @@ require mathlib from git
 lean_lib «HepLean» {
   -- add any library configuration options here
 }
+
+meta if get_config? env = some "dev" then -- dev is so not everyone has to build it
+require «doc-gen4» from git "https://github.com/leanprover/doc-gen4" @ "main"