diff --git a/clientapi/routing/joinroom.go b/clientapi/routing/joinroom.go
index 48e42214..2a2fce18 100644
--- a/clientapi/routing/joinroom.go
+++ b/clientapi/routing/joinroom.go
@@ -18,9 +18,11 @@ import (
 	"net/http"
 
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
+	"github.com/matrix-org/dendrite/clientapi/auth/storage/accounts"
 	"github.com/matrix-org/dendrite/clientapi/httputil"
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	roomserverAPI "github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
 )
 
@@ -28,6 +30,7 @@ func JoinRoomByIDOrAlias(
 	req *http.Request,
 	device *authtypes.Device,
 	rsAPI roomserverAPI.RoomserverInternalAPI,
+	accountDB accounts.Database,
 	roomIDOrAlias string,
 ) util.JSONResponse {
 	// Prepare to ask the roomserver to perform the room join.
@@ -44,6 +47,21 @@ func JoinRoomByIDOrAlias(
 		return *err
 	}
 
+	// Work out our localpart for the client profile request.
+	localpart, _, err := gomatrixserverlib.SplitID('@', device.UserID)
+	if err != nil {
+		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
+	} else {
+		// Request our profile content to populate the request content with.
+		profile, err := accountDB.GetProfileByLocalpart(req.Context(), localpart)
+		if err != nil {
+			util.GetLogger(req.Context()).WithError(err).Error("accountDB.GetProfileByLocalpart failed")
+		} else {
+			joinReq.Content["displayname"] = profile.DisplayName
+			joinReq.Content["avatar_url"] = profile.AvatarURL
+		}
+	}
+
 	// Ask the roomserver to perform the join.
 	if err := rsAPI.PerformJoin(req.Context(), &joinReq, &joinRes); err != nil {
 		return util.JSONResponse{
diff --git a/clientapi/routing/routing.go b/clientapi/routing/routing.go
index ead8a4c8..f8cdcf5b 100644
--- a/clientapi/routing/routing.go
+++ b/clientapi/routing/routing.go
@@ -100,7 +100,7 @@ func Setup(
 				return util.ErrorResponse(err)
 			}
 			return JoinRoomByIDOrAlias(
-				req, device, rsAPI, vars["roomIDOrAlias"],
+				req, device, rsAPI, accountDB, vars["roomIDOrAlias"],
 			)
 		}),
 	).Methods(http.MethodPost, http.MethodOptions)