diff --git a/modules/lang/ocaml/config.el b/modules/lang/ocaml/config.el
index 69ce17737..7772ef630 100644
--- a/modules/lang/ocaml/config.el
+++ b/modules/lang/ocaml/config.el
@@ -113,4 +113,9 @@
     (setq +format-with 'ocp-indent)
     (when (and (executable-find "ocamlformat")
                (locate-dominating-file default-directory ".ocamlformat"))
+      (let ((ext (file-name-extension buffer-file-name t)))
+        (cond ((equal ext ".eliom")
+               (setq-local ocamlformat-file-kind 'implementation))
+              ((equal ext ".eliomi")
+               (setq-local ocamlformat-file-kind 'interface))))
       (setq +format-with 'ocamlformat))))