diff --git a/pkg/client/client.go b/pkg/client/client.go
index 7568648..b276759 100644
--- a/pkg/client/client.go
+++ b/pkg/client/client.go
@@ -10,13 +10,6 @@ import (
 	"net/url"
 )
 
-// HTTPClient interface holds the required Post method
-// to send FleetLock requests.
-type HTTPClient interface {
-	// Do send a `body` payload to the URL.
-	Do(*http.Request) (*http.Response, error)
-}
-
 // Payload is the content to send
 // to the FleetLock server.
 type Payload struct {
@@ -40,7 +33,7 @@ type Client struct {
 	URL   string
 	group string
 	id    string
-	http  HTTPClient
+	http  *http.Client
 }
 
 func (c *Client) generateRequest(endpoint string) (*http.Request, error) {
@@ -129,7 +122,7 @@ func (c *Client) UnlockIfHeld() error {
 }
 
 // New builds a Fleet-Lock client.
-func New(URL, group, ID string, c HTTPClient) (*Client, error) {
+func New(URL, group, ID string, c *http.Client) (*Client, error) {
 	if _, err := url.ParseRequestURI(URL); err != nil {
 		return nil, fmt.Errorf("parsing URL: %w", err)
 	}
diff --git a/pkg/client/client_test.go b/pkg/client/client_test.go
index ae48200..48787e1 100644
--- a/pkg/client/client_test.go
+++ b/pkg/client/client_test.go
@@ -11,15 +11,15 @@ import (
 	"github.com/flatcar-linux/fleetlock/pkg/client"
 )
 
-type httpClient struct {
+type mockRoundTripper struct {
 	resp  *http.Response
 	r     *http.Request
 	doErr error
 }
 
-func (h *httpClient) Do(req *http.Request) (*http.Response, error) {
-	h.r = req
-	return h.resp, h.doErr
+func (r *mockRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	r.r = req
+	return r.resp, r.doErr
 }
 
 func TestBadURL(t *testing.T) {
@@ -61,11 +61,12 @@ func TestRecursiveLock(t *testing.T) {
 			expErr:     errors.New("unexpected status code: 100"),
 		},
 		{
-			expErr: errors.New("doing the request: connection refused"),
+			expErr: errors.New("doing the request: Post \"http://1.2.3.4/v1/pre-reboot\": connection refused"),
 			doErr:  errors.New("connection refused"),
 		},
 	} {
-		h := &httpClient{
+		h := http.DefaultClient
+		tr := &mockRoundTripper{
 			resp: &http.Response{
 				StatusCode: test.statusCode,
 				Body:       test.body,
@@ -73,6 +74,8 @@ func TestRecursiveLock(t *testing.T) {
 			doErr: test.doErr,
 		}
 
+		h.Transport = tr
+
 		c, _ := client.New("http://1.2.3.4", "default", "1234", h)
 
 		err := c.RecursiveLock()
@@ -80,8 +83,8 @@ func TestRecursiveLock(t *testing.T) {
 			t.Fatalf("should have %v for err, got: %v", test.expErr, err)
 		}
 
-		if h.r.URL.String() != expURL {
-			t.Fatalf("should have %s for URL, got: %s", expURL, h.r.URL.String())
+		if tr.r.URL.String() != expURL {
+			t.Fatalf("should have %s for URL, got: %s", expURL, tr.r.URL.String())
 		}
 	}
 }
@@ -114,11 +117,12 @@ func TestUnlockIfHeld(t *testing.T) {
 			expErr:     errors.New("unexpected status code: 100"),
 		},
 		{
-			expErr: errors.New("doing the request: connection refused"),
+			expErr: errors.New("doing the request: Post \"http://1.2.3.4/v1/steady-state\": connection refused"),
 			doErr:  errors.New("connection refused"),
 		},
 	} {
-		h := &httpClient{
+		h := http.DefaultClient
+		tr := &mockRoundTripper{
 			resp: &http.Response{
 				StatusCode: test.statusCode,
 				Body:       test.body,
@@ -126,6 +130,8 @@ func TestUnlockIfHeld(t *testing.T) {
 			doErr: test.doErr,
 		}
 
+		h.Transport = tr
+
 		c, _ := client.New("http://1.2.3.4", "default", "1234", h)
 
 		err := c.UnlockIfHeld()
@@ -133,8 +139,8 @@ func TestUnlockIfHeld(t *testing.T) {
 			t.Fatalf("should have %v for err, got: %v", test.expErr, err)
 		}
 
-		if h.r.URL.String() != expURL {
-			t.Fatalf("should have %s for URL, got: %s", expURL, h.r.URL.String())
+		if tr.r.URL.String() != expURL {
+			t.Fatalf("should have %s for URL, got: %s", expURL, tr.r.URL.String())
 		}
 	}
 }