diff --git a/src/net/http/pprof/pprof.go b/src/net/http/pprof/pprof.go
index 2357d8ed1e..44afa2d8d8 100644
--- a/src/net/http/pprof/pprof.go
+++ b/src/net/http/pprof/pprof.go
@@ -30,7 +30,8 @@
 //
 //	go tool pprof http://localhost:6060/debug/pprof/profile
 //
-// Or to look at the goroutine blocking profile:
+// Or to look at the goroutine blocking profile, after calling
+// runtime.SetBlockProfileRate in your program:
 //
 //	go tool pprof http://localhost:6060/debug/pprof/block
 //