diff --git a/src/testing/fuzz.go b/src/testing/fuzz.go
index 18f2b2f319..4a5def1ab4 100644
--- a/src/testing/fuzz.go
+++ b/src/testing/fuzz.go
@@ -22,8 +22,9 @@ func initFuzzFlags() {
 	matchFuzz = flag.String("test.fuzz", "", "run the fuzz test matching `regexp`")
 	flag.Var(&fuzzDuration, "test.fuzztime", "time to spend fuzzing; default is to run indefinitely")
 	flag.Var(&minimizeDuration, "test.fuzzminimizetime", "time to spend minimizing a value after finding a failing input")
-	fuzzCacheDir = flag.String("test.fuzzcachedir", "", "directory where interesting fuzzing inputs are stored")
-	isFuzzWorker = flag.Bool("test.fuzzworker", false, "coordinate with the parent process to fuzz random values")
+
+	fuzzCacheDir = flag.String("test.fuzzcachedir", "", "directory where interesting fuzzing inputs are stored (for use only by cmd/go)")
+	isFuzzWorker = flag.Bool("test.fuzzworker", false, "coordinate with the parent process to fuzz random values (for use only by cmd/go)")
 }
 
 var (