diff --git a/ca/acmeClient.go b/ca/acmeClient.go
index 28451a45..cca35b93 100644
--- a/ca/acmeClient.go
+++ b/ca/acmeClient.go
@@ -37,15 +37,18 @@ func NewACMEClient(endpoint string, contact []string, opts ...ClientOption) (*AC
 	if err != nil {
 		return nil, err
 	}
-
 	ac := &ACMEClient{
 		client: &http.Client{
 			Transport: tr,
 		},
 		dirLoc: endpoint,
 	}
-
-	resp, err := ac.client.Get(endpoint)
+	req, err := http.NewRequest("GET", endpoint, http.NoBody)
+	if err != nil {
+		return nil, errors.Wrapf(err, "creating GET request %s failed", endpoint)
+	}
+	req.Header.Set("User-Agent", UserAgent)
+	resp, err := ac.client.Do(req)
 	if err != nil {
 		return nil, errors.Wrapf(err, "client GET %s failed", endpoint)
 	}
@@ -99,7 +102,12 @@ func (c *ACMEClient) GetDirectory() (*acmeAPI.Directory, error) {
 // GetNonce makes a nonce request to the ACME api and returns an
 // ACME directory object.
 func (c *ACMEClient) GetNonce() (string, error) {
-	resp, err := c.client.Get(c.dir.NewNonce)
+	req, err := http.NewRequest("GET", c.dir.NewNonce, http.NoBody)
+	if err != nil {
+		return "", errors.Wrapf(err, "creating GET request %s failed", c.dir.NewNonce)
+	}
+	req.Header.Set("User-Agent", UserAgent)
+	resp, err := c.client.Do(req)
 	if err != nil {
 		return "", errors.Wrapf(err, "client GET %s failed", c.dir.NewNonce)
 	}
@@ -171,9 +179,15 @@ func (c *ACMEClient) post(payload []byte, url string, headerOps ...withHeaderOpt
 	if err != nil {
 		return nil, err
 	}
-	resp, err := c.client.Post(url, "application/jose+json", strings.NewReader(raw))
+	req, err := http.NewRequest("POST", url, strings.NewReader(raw))
+	if err != nil {
+		return nil, errors.Wrapf(err, "creating POST request %s failed", url)
+	}
+	req.Header.Set("Content-Type", "application/jose+json")
+	req.Header.Set("User-Agent", UserAgent)
+	resp, err := c.client.Do(req)
 	if err != nil {
-		return nil, errors.Wrapf(err, "client GET %s failed", c.dir.NewOrder)
+		return nil, errors.Wrapf(err, "client POST %s failed", c.dir.NewOrder)
 	}
 	return resp, nil
 }
diff --git a/ca/acmeClient_test.go b/ca/acmeClient_test.go
index d22c4972..ad5f2116 100644
--- a/ca/acmeClient_test.go
+++ b/ca/acmeClient_test.go
@@ -109,6 +109,7 @@ func TestNewACMEClient(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
 				switch {
 				case i == 0:
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -203,6 +204,7 @@ func TestACMEClient_GetNonce(t *testing.T) {
 			tc := run(t)
 
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				api.JSONStatus(w, tc.r1, tc.rc1)
 			})
@@ -309,6 +311,8 @@ func TestACMEClient_post(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -447,6 +451,8 @@ func TestACMEClient_NewOrder(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -567,6 +573,8 @@ func TestACMEClient_GetOrder(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -687,6 +695,8 @@ func TestACMEClient_GetAuthz(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -807,6 +817,8 @@ func TestACMEClient_GetChallenge(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -928,6 +940,8 @@ func TestACMEClient_ValidateChallenge(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -1053,6 +1067,8 @@ func TestACMEClient_FinalizeOrder(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -1180,6 +1196,8 @@ func TestACMEClient_GetAccountOrders(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)
@@ -1309,6 +1327,8 @@ func TestACMEClient_GetCertificate(t *testing.T) {
 
 			i := 0
 			srv.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				assert.Equals(t, "step-http-client/1.0", req.Header.Get("User-Agent")) // check default User-Agent header
+
 				w.Header().Set("Replay-Nonce", expectedNonce)
 				if i == 0 {
 					api.JSONStatus(w, tc.r1, tc.rc1)