diff --git a/internal/client/client.go b/internal/client/client.go
index 9dde9516..2accca90 100644
--- a/internal/client/client.go
+++ b/internal/client/client.go
@@ -459,6 +459,53 @@ func (c *CSAPI) LoginUser(t *testing.T, localpart, password string, opts ...Logi
 	return userID, accessToken, deviceID
 }
 
+// LoginUserWithRefreshToken will log in to a homeserver, with refresh token enabled,
+// and create a new device on an existing user.
+func (c *CSAPI) LoginUserWithRefreshToken(t *testing.T, localpart, password string) (userID, accessToken, refreshToken, deviceID string, expiresInMs int64) {
+	t.Helper()
+	reqBody := map[string]interface{}{
+		"identifier": map[string]interface{}{
+			"type": "m.id.user",
+			"user": localpart,
+		},
+		"password":      password,
+		"type":          "m.login.password",
+		"refresh_token": true,
+	}
+	res := c.MustDoFunc(t, "POST", []string{"_matrix", "client", "v3", "login"}, WithJSONBody(t, reqBody))
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatalf("unable to read response body: %v", err)
+	}
+
+	userID = gjson.GetBytes(body, "user_id").Str
+	accessToken = gjson.GetBytes(body, "access_token").Str
+	deviceID = gjson.GetBytes(body, "device_id").Str
+	refreshToken = gjson.GetBytes(body, "refresh_token").Str
+	expiresInMs = gjson.GetBytes(body, "expires_in_ms").Int()
+	return userID, accessToken, refreshToken, deviceID, expiresInMs
+}
+
+// RefreshToken will consume a refresh token and return a new access token and refresh token.
+func (c *CSAPI) ConsumeRefreshToken(t *testing.T, refreshToken string) (newAccessToken, newRefreshToken string, expiresInMs int64) {
+	t.Helper()
+	reqBody := map[string]interface{}{
+		"refresh_token": refreshToken,
+	}
+	res := c.MustDoFunc(t, "POST", []string{"_matrix", "client", "v3", "refresh"}, WithJSONBody(t, reqBody))
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatalf("unable to read response body: %v", err)
+	}
+
+	newAccessToken = gjson.GetBytes(body, "access_token").Str
+	newRefreshToken = gjson.GetBytes(body, "refresh_token").Str
+	expiresInMs = gjson.GetBytes(body, "expires_in_ms").Int()
+	return newAccessToken, newRefreshToken, expiresInMs
+}
+
 // RegisterUser will register the user with given parameters and
 // return user ID, access token and device ID. It fails the test on network error.
 func (c *CSAPI) RegisterUser(t *testing.T, localpart, password string) (userID, accessToken, deviceID string) {
diff --git a/tests/csapi/txnid_test.go b/tests/csapi/txnid_test.go
index 01c055dd..8aca4006 100644
--- a/tests/csapi/txnid_test.go
+++ b/tests/csapi/txnid_test.go
@@ -213,3 +213,52 @@ func TestTxnIdempotency(t *testing.T) {
 
 	must.NotEqualStr(t, eventID4, eventID3, "Expected eventID4 and eventID3 to be different, but they were not")
 }
+
+// TestTxnAfterRefresh tests that when a client refreshes its access token,
+// it still gets back a transaction ID in the sync response.
+func TestTxnAfterRefresh(t *testing.T) {
+  // Dendrite and Conduit don't support refresh tokens yet.
+	// Synapse has a broken implementation of refresh tokens: https://github.com/matrix-org/synapse/issues/15141
+  runtime.SkipIf(t, runtime.Dendrite, runtime.Conduit, runtime.Synapse)
+
+  deployment := Deploy(t, b.BlueprintCleanHS)
+  defer deployment.Destroy(t)
+
+  deployment.RegisterUser(t, "hs1", "alice", "password", false)
+
+  c := deployment.Client(t, "hs1", "")
+
+  var refreshToken string
+  c.UserID, c.AccessToken, refreshToken, c.DeviceID, _ = c.LoginUserWithRefreshToken(t, "alice", "password")
+
+  // Create a room where we can send events.
+  roomID := c.CreateRoom(t, map[string]interface{}{})
+
+	txnId := "abcdef"
+  // Let's send an event, and wait for it to appear in the sync.
+  eventID := c.SendEventUnsyncedWithTxnID(t, roomID, b.Event{
+    Type: "m.room.message",
+    Content: map[string]interface{}{
+      "msgtype": "m.text",
+      "body":    "first",
+    },
+  }, txnId)
+
+  // When syncing, we should find the event and it should have a transaction ID.
+  token := c.MustSyncUntil(t, client.SyncReq{}, mustHaveTransactionIDForEvent(t, roomID, eventID, txnId))
+
+  // Now do the same, but refresh the token before syncing.
+  eventID = c.SendEventUnsyncedWithTxnID(t, roomID, b.Event{
+    Type: "m.room.message",
+    Content: map[string]interface{}{
+      "msgtype": "m.text",
+      "body":    "second",
+    },
+  }, txnId)
+
+  // Use the refresh token to get a new access token.
+  c.AccessToken, refreshToken, _ = c.ConsumeRefreshToken(t, refreshToken)
+
+  // When syncing, we should find the event and it should also have a transaction ID.
+  c.MustSyncUntil(t, client.SyncReq{Since: token}, mustHaveTransactionIDForEvent(t, roomID, eventID, txnId))
+}