diff --git a/src/core/CCString.mli b/src/core/CCString.mli
index 3cca9365..e280c381 100644
--- a/src/core/CCString.mli
+++ b/src/core/CCString.mli
@@ -184,11 +184,13 @@ val take : int -> string -> string
 
 val take_while : (char -> bool) -> string -> string
 (** [take_while p s] keeps only the longest prefix [t] of [s] such that every
-    character [c] in [t] satisfies [p c]. *)
+    character [c] in [t] satisfies [p c].
+    @since 3.16 *)
 
 val rtake_while : (char -> bool) -> string -> string
 (** [rtake_while p s] keeps only the longest suffix [t] of [s] such that every
-    character [c] in [t] satisfies [p c]. *)
+    character [c] in [t] satisfies [p c].
+    @since 3.16 *)
 
 val drop : int -> string -> string
 (** [drop n s] removes the [n] first chars of [s].
diff --git a/src/core/CCStringLabels.mli b/src/core/CCStringLabels.mli
index 318e8237..a3d4f358 100644
--- a/src/core/CCStringLabels.mli
+++ b/src/core/CCStringLabels.mli
@@ -193,6 +193,16 @@ val take : int -> string -> string
 (** [take n s] keeps only the [n] first chars of [s].
     @since 0.17 *)
 
+val take_while : p:(char -> bool) -> string -> string
+(** [take_while ~p s] keeps only the longest prefix [t] of [s] such that every
+    character [c] in [t] satisfies [p c].
+    @since 3.16 *)
+
+val rtake_while : p:(char -> bool) -> string -> string
+(** [rtake_while ~p s] keeps only the longest suffix [t] of [s] such that every
+    character [c] in [t] satisfies [p c].
+    @since 3.16 *)
+
 val drop : int -> string -> string
 (** [drop n s] removes the [n] first chars of [s].
     @since 0.17 *)