diff --git a/src/core/CCVector.ml b/src/core/CCVector.ml
index 4f90df11..3bf6ab51 100644
--- a/src/core/CCVector.ml
+++ b/src/core/CCVector.ml
@@ -129,7 +129,7 @@ let grow_with_ v ~filler:x =
   ) else (
     let n = Array.length v.vec in
     let size = min (2 * n + 3) Sys.max_array_length in
-    if size = n then failwith "vec: can't grow any further";
+    if size = n then invalid_arg "vec: can't grow any further";
     resize_ v size v.vec.(0)
   )
 
@@ -139,7 +139,7 @@ let grow_with_ v ~filler:x =
    behave well *)
 let ensure_assuming_not_empty_ v ~size =
   if size > Sys.max_array_length
-  then failwith "vec.ensure: size too big"
+  then invalid_arg "vec.ensure: size too big"
   else (
     let n = ref (max 8 (Array.length v.vec)) in
     while !n < size do n := min Sys.max_array_length (2* !n) done;
diff --git a/src/core/CCVector.mli b/src/core/CCVector.mli
index 17170a7c..88a9edcb 100644
--- a/src/core/CCVector.mli
+++ b/src/core/CCVector.mli
@@ -66,12 +66,15 @@ val ensure_with : init:'a -> ('a, rw) t -> int -> unit
     This does not affect [length v].
     @param init if [capacity v = 0], used to enforce the type of the vector
       (see {!create_with}).
+    @raise Invalid_arg if the size is not suitable (negative, or too big for OCaml arrays)
     @since 0.14 *)
 
 val ensure : ('a, rw) t -> int -> unit
 (** Hint to the vector that it should have at least the given capacity.
     Just a hint, will not be enforced if the vector is empty and [init]
-      is not provided. *)
+    is not provided.
+    @raise Invalid_arg if the size is not suitable (negative, or too big for OCaml arrays)
+*)
 
 val is_empty : ('a, _) t -> bool
 (** Is the vector empty? *)
@@ -114,7 +117,7 @@ val pop : ('a, rw) t -> 'a option
 (** Remove last element, or [None]. *)
 
 val pop_exn : ('a, rw) t -> 'a
-(** Remove last element, or raise a Failure if empty.
+(** Remove last element, or raise an exception if empty.
     @raise Empty on an empty vector. *)
 
 val top : ('a, _) t -> 'a option