diff --git a/lib/Conf.ml b/lib/Conf.ml
index f99ad5ae6e..dfd1ebc121 100644
--- a/lib/Conf.ml
+++ b/lib/Conf.ml
@@ -96,6 +96,7 @@ let conventional_profile from =
   ; parens_ite= elt false
   ; parens_tuple= elt `Always
   ; parens_tuple_patterns= elt `Multi_line_only
+  ; parens_tuple_labeled_arg_types= elt false
   ; parse_docstrings= elt true
   ; parse_toplevel_phrases= elt false
   ; sequence_blank_line= elt `Preserve_one
@@ -164,6 +165,7 @@ let ocamlformat_profile from =
   ; parens_ite= elt false
   ; parens_tuple= elt `Always
   ; parens_tuple_patterns= elt `Multi_line_only
+  ; parens_tuple_labeled_arg_types= elt false
   ; parse_docstrings= elt false
   ; parse_toplevel_phrases= elt false
   ; sequence_blank_line= elt `Compact
@@ -231,6 +233,7 @@ let janestreet_profile from =
   ; parens_ite= elt true
   ; parens_tuple= elt `Multi_line_only
   ; parens_tuple_patterns= elt `Multi_line_only
+  ; parens_tuple_labeled_arg_types= elt true
   ; parse_docstrings= elt false
   ; parse_toplevel_phrases= elt false
   ; sequence_blank_line= elt `Compact
diff --git a/lib/Conf_t.ml b/lib/Conf_t.ml
index 59f0c6b458..d5b13545f6 100644
--- a/lib/Conf_t.ml
+++ b/lib/Conf_t.ml
@@ -104,6 +104,7 @@ type fmt_opts =
   ; parens_ite: bool elt
   ; parens_tuple: [`Always | `Multi_line_only] elt
   ; parens_tuple_patterns: [`Always | `Multi_line_only] elt
+  ; parens_tuple_labeled_arg_types: bool elt
   ; parse_docstrings: bool elt
   ; parse_toplevel_phrases: bool elt
   ; sequence_blank_line: [`Compact | `Preserve_one] elt
diff --git a/lib/Conf_t.mli b/lib/Conf_t.mli
index 853e321d8e..82c63b98d9 100644
--- a/lib/Conf_t.mli
+++ b/lib/Conf_t.mli
@@ -102,6 +102,7 @@ type fmt_opts =
   ; parens_ite: bool elt
   ; parens_tuple: [`Always | `Multi_line_only] elt
   ; parens_tuple_patterns: [`Always | `Multi_line_only] elt
+  ; parens_tuple_labeled_arg_types: bool elt
   ; parse_docstrings: bool elt
   ; parse_toplevel_phrases: bool elt
   ; sequence_blank_line: [`Compact | `Preserve_one] elt
diff --git a/lib/Fmt_ast.ml b/lib/Fmt_ast.ml
index e1d6ff5c37..fbf0dba991 100644
--- a/lib/Fmt_ast.ml
+++ b/lib/Fmt_ast.ml
@@ -801,9 +801,15 @@ and fmt_arrow_param ~return c ctx
     | Ptyp_tuple ((Some _, _) :: _) -> true
     | _ -> false
   in
-  let core_type =
-    Params.parens_if labeled_tuple_ret_parens c.conf (fmt_core_type c xtI)
+  (* Jane Street: With our profile only, parenthesize the body of a labeled
+     parameter type if it is a tuple, to distinguish from labeled tuples. *)
+  let labeled_arg_tuple_parens =
+    c.conf.fmt_opts.parens_tuple_labeled_arg_types.v && (not return)
+    && (match tI.ptyp_desc with Ptyp_tuple _ -> true | _ -> false)
+    && match lI with Nolabel -> false | Labelled _ | Optional _ -> true
   in
+  let parens = labeled_tuple_ret_parens || labeled_arg_tuple_parens in
+  let core_type = fmt_core_type ~parens c xtI in
   let arg =
     match arg_label lI with
     | None -> core_type
@@ -849,7 +855,7 @@ and fmt_arrow_type c ~ctx ?indent ~parens ~parent_has_parens args fmt_ret_typ
    gets support for them, we should remove tydecl_param and go with whatever
    their solution is. *)
 and fmt_core_type c ?(box = true) ?pro ?(pro_space = true) ?constraint_ctx
-    ?(tydecl_param = false) ({ast= typ; ctx} as xtyp) =
+    ?(tydecl_param = false) ?(parens = false) ({ast= typ; ctx} as xtyp) =
   protect c (Typ typ)
   @@
   let {ptyp_desc; ptyp_attributes; ptyp_loc; _} = typ in
@@ -883,7 +889,7 @@ and fmt_core_type c ?(box = true) ?pro ?(pro_space = true) ?constraint_ctx
              (Params.parens_if (not tydecl_param) c.conf
                 (k $ fmt_attributes c ~pre:Cut atrs) ) )
   @@
-  let parens = (not tydecl_param) && parenze_typ xtyp in
+  let parens = parens || ((not tydecl_param) && parenze_typ xtyp) in
   hvbox_if box 0
   @@ Params.parens_if
        (match typ.ptyp_desc with Ptyp_tuple _ -> false | _ -> parens)
diff --git a/test/passing/tests/labeled_tuples.ml b/test/passing/tests/labeled_tuples.ml
index cd94542c96..942937b2a1 100644
--- a/test/passing/tests/labeled_tuples.ml
+++ b/test/passing/tests/labeled_tuples.ml
@@ -269,3 +269,16 @@ let _ = f (Foo (~x:5, 1))
 let _ = f (Foo (5, 1))
 let _ = f (Foo (5, ~x:1))
 let _ = f (Foo (5, ~y:1))
+
+(* As a result of labeled tuples, we've decided to add parens around labeled function
+   argument types when they are tuples, for disambiguation. *)
+type t = x:(int * bool) -> string
+type t = x:(int * y:bool) -> string
+type t = x:(y:int * z:bool) -> string
+
+type t =
+  x:
+    (long_type_name_for_multiline1
+    * long_type_name_for_multiline2
+    * long_type_name_for_multiline3)
+  -> string
diff --git a/test/passing/tests/labeled_tuples_regressions.mli b/test/passing/tests/labeled_tuples_regressions.mli
index 63f6dc92fb..90b2b33aa7 100644
--- a/test/passing/tests/labeled_tuples_regressions.mli
+++ b/test/passing/tests/labeled_tuples_regressions.mli
@@ -1,6 +1,6 @@
 (* https://github.com/janestreet/ocamlformat/pull/49 *)
 val f
-  :  foo:int * very_long_type_name_so_we_get_multiple_lines
+  :  foo:(int * very_long_type_name_so_we_get_multiple_lines)
   -> (* cmt *)
      bar:('long_type_var_1, 'long_type_var_2) Long_module_name.t
   -> additional_somewhat_long_type_name