diff --git a/config.go b/config.go
index d799c5ff..644aaac8 100644
--- a/config.go
+++ b/config.go
@@ -72,7 +72,7 @@ func (s *FullJitterStrategy) Calculate(attempt int) time.Duration {
 
 	backoffDuration := s.cfg.BackoffMultiplier *
 		time.Duration(math.Pow(2, float64(attempt)))
-	return time.Duration(s.rng.Intn(int(backoffDuration)))
+	return time.Duration(s.rng.Int63n(int64(backoffDuration)))
 }
 
 func (s *FullJitterStrategy) setConfig(cfg *Config) {
diff --git a/config_test.go b/config_test.go
index 060b0739..791c2c23 100644
--- a/config_test.go
+++ b/config_test.go
@@ -80,8 +80,8 @@ func TestExponentialBackoff(t *testing.T) {
 
 func TestFullJitterBackoff(t *testing.T) {
 	expected := []time.Duration{
-		566028617 * time.Nanosecond,
-		1365407263 * time.Nanosecond,
+		724039541 * time.Nanosecond,
+		1603903257 * time.Nanosecond,
 		5232470547 * time.Nanosecond,
 		21467499218 * time.Nanosecond,
 	}