diff --git a/src/core/CCHeap.ml b/src/core/CCHeap.ml
index 4917db07..b85ce53f 100644
--- a/src/core/CCHeap.ml
+++ b/src/core/CCHeap.ml
@@ -119,8 +119,11 @@ module type S = sig
       @raise Empty if the heap is empty *)
 
   val delete_all : (elt -> elt -> bool) -> elt -> t -> t
-  (** Delete value if it exist in the heap.
-      [delete_all eq x h], use [eq] to find all [x] in [h] and delete them *)
+  (** Delete all occurrences of a value in the heap.
+      [delete_all eq x h], use [eq] to find all [x] in [h] and delete them.
+      If [h] do not contain [x] then it return [h].
+      The difference with {!filter} is that [delete_all] stops as soon as
+      it enters a subtree whose root is bigger than the element *)
 
   val iter : (elt -> unit) -> t -> unit
   (** Iterate on elements *)
diff --git a/src/core/CCHeap.mli b/src/core/CCHeap.mli
index dca9f91e..ac320aef 100644
--- a/src/core/CCHeap.mli
+++ b/src/core/CCHeap.mli
@@ -56,8 +56,11 @@ module type S = sig
       @raise Empty if the heap is empty *)
 
   val delete_all : (elt -> elt -> bool) -> elt -> t -> t
-  (** Delete value if it exist in the heap.
-      [delete_all eq x h], use [eq] to find all [x] in [h] and delete them
+  (** Delete all occurrences of a value in the heap.
+      [delete_all eq x h], use [eq] to find all [x] in [h] and delete them.
+      If [h] do not contain [x] then it return [h].
+      The difference with {!filter} is that [delete_all] stops as soon as
+      it enters a subtree whose root is bigger than the element
       @since NEXT_RELEASE *)
 
   val iter : (elt -> unit) -> t -> unit