diff --git a/hphp/hack/.gitignore b/hphp/hack/.gitignore
index deb01ee9ca4ee3..d6b43ad4086b37 100644
--- a/hphp/hack/.gitignore
+++ b/hphp/hack/.gitignore
@@ -19,6 +19,7 @@ facebook/opam2-mini-repository-*
 facebook/opam2-mini-repository-*.tar.gz
 target/
 dev_env.sh
+.merlin
 # Generated by scripts/build_rust_to_ocaml.sh; the script can't delete it
 # without creating a race condition when we're doing parallel builds.
 #