diff --git a/client.go b/client.go
index b3bd9158..294595f8 100644
--- a/client.go
+++ b/client.go
@@ -1581,12 +1581,27 @@ func (cli *Client) DownloadBytes(ctx context.Context, mxcURL id.ContentURI) ([]b
 	return io.ReadAll(resp.Body)
 }
 
+type ReqCreateMXC struct {
+	BeeperUniqueID string
+	BeeperRoomID   id.RoomID
+}
+
 // CreateMXC creates a blank Matrix content URI to allow uploading the content asynchronously later.
 //
 // See https://spec.matrix.org/v1.7/client-server-api/#post_matrixmediav1create
-func (cli *Client) CreateMXC(ctx context.Context) (*RespCreateMXC, error) {
+func (cli *Client) CreateMXC(ctx context.Context, extra ...ReqCreateMXC) (*RespCreateMXC, error) {
 	var m RespCreateMXC
-	_, err := cli.MakeRequest(ctx, http.MethodPost, cli.BuildURL(MediaURLPath{"v1", "create"}), nil, &m)
+	query := map[string]string{}
+	if len(extra) > 0 {
+		if extra[0].BeeperUniqueID != "" {
+			query["com.beeper.unique_id"] = extra[0].BeeperUniqueID
+		}
+		if extra[0].BeeperRoomID != "" {
+			query["com.beeper.room_id"] = string(extra[0].BeeperRoomID)
+		}
+	}
+	createURL := cli.BuildURLWithQuery(MediaURLPath{"v1", "create"}, query)
+	_, err := cli.MakeRequest(ctx, http.MethodPost, createURL, nil, &m)
 	return &m, err
 }
 
diff --git a/responses.go b/responses.go
index 9e5fd0aa..26aaac77 100644
--- a/responses.go
+++ b/responses.go
@@ -111,10 +111,14 @@ type RespMediaUpload struct {
 
 // RespCreateMXC is the JSON response for https://spec.matrix.org/v1.7/client-server-api/#post_matrixmediav1create
 type RespCreateMXC struct {
-	ContentURI      id.ContentURI `json:"content_uri"`
-	UnusedExpiresAt int           `json:"unused_expires_at,omitempty"`
+	ContentURI      id.ContentURI      `json:"content_uri"`
+	UnusedExpiresAt jsontime.UnixMilli `json:"unused_expires_at,omitempty"`
 
 	UnstableUploadURL string `json:"com.beeper.msc3870.upload_url,omitempty"`
+
+	// Beeper extensions for uploading unique media only once
+	BeeperUniqueID    string             `json:"com.beeper.unique_id,omitempty"`
+	BeeperCompletedAt jsontime.UnixMilli `json:"com.beeper.completed_at,omitempty"`
 }
 
 // RespPreviewURL is the JSON response for https://spec.matrix.org/v1.2/client-server-api/#get_matrixmediav3preview_url