diff --git a/lib/pure/collections/intsets.nim b/lib/pure/collections/intsets.nim
index b46e040ca..7520e6e46 100644
--- a/lib/pure/collections/intsets.nim
+++ b/lib/pure/collections/intsets.nim
@@ -191,9 +191,10 @@ proc `$`*(s: IntSet): string =
   ## The `$` operator for int sets.
   dollarImpl()
 
-proc empty*(s: IntSet): bool {.inline.} =
+proc empty*(s: IntSet): bool {.inline, deprecated.} =
   ## returns true if `s` is empty. This is safe to call even before
-  ## the set has been initialized with `initIntSet`.
+  ## the set has been initialized with `initIntSet`. Note this never
+  ## worked reliably and so is deprecated.
   result = s.counter == 0
 
 when isMainModule: