diff --git a/src/libraries/utils/result.mli b/src/libraries/utils/result.mli
index abbdeb65b2dc22aa8958b42972f9f168bc25fb6f..0411390df5fcbf37e1d0977f3a46697c7547bc12 100644
--- a/src/libraries/utils/result.mli
+++ b/src/libraries/utils/result.mli
@@ -25,6 +25,9 @@
 
 include module type of Stdlib.Result
 
+(** [zip r1 r2] regroups values in a pair [Ok (v1, v2)] if both arguments are
+    [Ok v1] and [Ok v2] and propagate errors in other cases. If both [r1]
+    and [r2] are errors we keep the first one, in this case [r1]. *)
 val zip : ('a, 'e) result -> ('b, 'e) result -> ('a * 'b, 'e) result
 
 module Operators : sig