diff --git a/src/runtime/mprof.go b/src/runtime/mprof.go
index 259473c9ce..0455fe86ac 100644
--- a/src/runtime/mprof.go
+++ b/src/runtime/mprof.go
@@ -434,7 +434,7 @@ var mutexprofilerate uint64 // fraction sampled
 // reported. The previous rate is returned.
 //
 // To turn off profiling entirely, pass rate 0.
-// To just read the current rate, pass rate -1.
+// To just read the current rate, pass rate < 0.
 // (For n>1 the details of sampling may change.)
 func SetMutexProfileFraction(rate int) int {
 	if rate < 0 {