diff --git a/expr/func_keeplastvalue.go b/expr/func_keeplastvalue.go
index 8a4e7ea75e..f3a92e0bc8 100644
--- a/expr/func_keeplastvalue.go
+++ b/expr/func_keeplastvalue.go
@@ -25,8 +25,8 @@ func (s *FuncKeepLastValue) Signature() ([]Arg, []Arg) {
 				opt: true,
 				args: []Arg{
 					ArgInt{val: &s.limit},
-					// Allow user to specify 'INF' as value. if so, will fall back to maxInt
-					// Ignores any other strings (just like Graphite)
+					// Treats any string as infinity. This matches Graphite's behavior
+					// (although intended bevahior is to let user specify "INF" as the limit)
 					ArgString{val: &stub},
 				},
 			},