diff --git a/contacts.go b/contacts.go
index 1748485..f88ff30 100644
--- a/contacts.go
+++ b/contacts.go
@@ -183,6 +183,7 @@ type UpdateContactRequest struct {
 	UserID            string
 	FirstName         string
 	LastName          string
+	Source            string
 	Subscribed        *bool
 	UserGroup         string
 	MailingLists      map[string]bool
@@ -198,6 +199,9 @@ func (c *Client) UpdateContact(req UpdateContactRequest) error {
 	if req.UserID != "" {
 		body["userId"] = req.UserID
 	}
+	if req.Source != "" {
+		body["source"] = req.Source
+	}
 
 	b, err := json.Marshal(body)
 	if err != nil {
diff --git a/contacts_test.go b/contacts_test.go
index e611e15..c01c370 100644
--- a/contacts_test.go
+++ b/contacts_test.go
@@ -277,6 +277,7 @@ func TestUpdateContact(t *testing.T) {
 				Email:      "bob@example.com",
 				FirstName:  "Bob",
 				LastName:   "Smith",
+				Source:     "api",
 				Subscribed: boolPtr(false),
 				UserGroup:  "vip",
 			},
@@ -286,6 +287,7 @@ func TestUpdateContact(t *testing.T) {
 				"email":      "bob@example.com",
 				"firstName":  "Bob",
 				"lastName":   "Smith",
+				"source":     "api",
 				"subscribed": false,
 				"userGroup":  "vip",
 			},