diff --git a/api/client.go b/api/client.go
index 5cd96280b90a..28bfc017fdb8 100644
--- a/api/client.go
+++ b/api/client.go
@@ -267,6 +267,9 @@ func NewClient(c *Config) (*Client, error) {
 	if c.HttpClient == nil {
 		c.HttpClient = DefaultConfig().HttpClient
 	}
+	if c.HttpClient.Transport == nil {
+		c.HttpClient.Transport = cleanhttp.DefaultTransport()
+	}
 
 	tp := c.HttpClient.Transport.(*http.Transport)
 	if err := http2.ConfigureTransport(tp); err != nil {
diff --git a/api/client_test.go b/api/client_test.go
index 84663eea8885..2dc89a86aa06 100644
--- a/api/client_test.go
+++ b/api/client_test.go
@@ -37,6 +37,15 @@ func TestDefaultConfig_envvar(t *testing.T) {
 	}
 }
 
+func TestClientDefaultHttpClient(t *testing.T) {
+	_, err := NewClient(&Config{
+		HttpClient: http.DefaultClient,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestClientNilConfig(t *testing.T) {
 	client, err := NewClient(nil)
 	if err != nil {