diff --git a/src/core/CCString.mli b/src/core/CCString.mli
index 519c42a5..3cca9365 100644
--- a/src/core/CCString.mli
+++ b/src/core/CCString.mli
@@ -184,11 +184,11 @@ 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 [f c]. *)
+    character [c] in [t] satisfies [p c]. *)
 
 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 [f c]. *)
+    character [c] in [t] satisfies [p c]. *)
 
 val drop : int -> string -> string
 (** [drop n s] removes the [n] first chars of [s].