diff --git a/provider_client_test.go b/provider_client_test.go
index b260246..8fd20f8 100644
--- a/provider_client_test.go
+++ b/provider_client_test.go
@@ -14,3 +14,22 @@
 	actual := p.AuthenticatedHeaders()
 	th.CheckDeepEquals(t, expected, actual)
 }
+
+func TestUserAgent(t *testing.T) {
+	p := &ProviderClient{}
+
+	p.UserAgent.Prepend("custom-user-agent/v2.4")
+	expected := "custom-user-agent/v2.4 gophercloud/v1.0"
+	actual := p.UserAgent.Join()
+	th.CheckEquals(t, expected, actual)
+
+	p.UserAgent.Prepend("another-custom-user-agent/v0.3", "a-third-ua/v5.9")
+	expected = "another-custom-user-agent/v0.3 a-third-ua/v5.9 custom-user-agent/v2.4 gophercloud/v1.0"
+	actual = p.UserAgent.Join()
+	th.CheckEquals(t, expected, actual)
+
+	p.UserAgent = UserAgent{}
+	expected = "gophercloud/v1.0"
+	actual = p.UserAgent.Join()
+	th.CheckEquals(t, expected, actual)
+}