diff --git a/clientapi/routing/joinroom.go b/clientapi/routing/joinroom.go
index 2d8f78fd2..0f1a9ba4d 100644
--- a/clientapi/routing/joinroom.go
+++ b/clientapi/routing/joinroom.go
@@ -242,6 +242,9 @@ func (r joinRoomReq) joinRoomUsingServers(
 	queryRes := roomserverAPI.QueryLatestEventsAndStateResponse{}
 	event, err := common.BuildEvent(r.req.Context(), &eb, r.cfg, r.evTime, r.queryAPI, &queryRes)
 	if err == nil {
+		// If we have successfully built an event at this point then we can
+		// assert that the room is a local room, as BuildEvent was able to
+		// add prev_events etc successfully.
 		if _, err = r.producer.SendEvents(
 			r.req.Context(),
 			[]gomatrixserverlib.HeaderedEvent{
@@ -260,6 +263,10 @@ func (r joinRoomReq) joinRoomUsingServers(
 			}{roomID},
 		}
 	}
+
+	// Otherwise, if we've reached here, then we haven't been able to populate
+	// prev_events etc for the room, therefore the room is probably federated.
+
 	// TODO: This needs to be re-thought, as in the case of an invite, the room
 	// will exist in the database in roomserver_rooms but won't have any state
 	// events, therefore this below check fails.
diff --git a/common/events.go b/common/events.go
index f4013dff9..adbdf3389 100644
--- a/common/events.go
+++ b/common/events.go
@@ -17,6 +17,7 @@ package common
 import (
 	"context"
 	"errors"
+	"fmt"
 	"time"
 
 	"github.com/matrix-org/dendrite/common/config"
@@ -46,6 +47,7 @@ func BuildEvent(
 
 	err := AddPrevEventsToEvent(ctx, builder, queryAPI, queryRes)
 	if err != nil {
+		// This can pass through a ErrRoomNoExists to the caller
 		return nil, err
 	}
 
@@ -68,7 +70,7 @@ func AddPrevEventsToEvent(
 ) error {
 	eventsNeeded, err := gomatrixserverlib.StateNeededForEventBuilder(builder)
 	if err != nil {
-		return err
+		return fmt.Errorf("gomatrixserverlib.StateNeededForEventBuilder: %w", err)
 	}
 
 	// Ask the roomserver for information about this room
@@ -77,7 +79,7 @@ func AddPrevEventsToEvent(
 		StateToFetch: eventsNeeded.Tuples(),
 	}
 	if err = queryAPI.QueryLatestEventsAndState(ctx, &queryReq, queryRes); err != nil {
-		return err
+		return fmt.Errorf("queryAPI.QueryLatestEventsAndState: %w", err)
 	}
 
 	if !queryRes.RoomExists {
@@ -86,7 +88,7 @@ func AddPrevEventsToEvent(
 
 	eventFormat, err := queryRes.RoomVersion.EventFormat()
 	if err != nil {
-		return err
+		return fmt.Errorf("queryRes.RoomVersion.EventFormat: %w", err)
 	}
 
 	builder.Depth = queryRes.Depth
@@ -96,13 +98,13 @@ func AddPrevEventsToEvent(
 	for i := range queryRes.StateEvents {
 		err = authEvents.AddEvent(&queryRes.StateEvents[i].Event)
 		if err != nil {
-			return err
+			return fmt.Errorf("authEvents.AddEvent: %w", err)
 		}
 	}
 
 	refs, err := eventsNeeded.AuthEventReferences(&authEvents)
 	if err != nil {
-		return err
+		return fmt.Errorf("eventsNeeded.AuthEventReferences: %w", err)
 	}
 
 	truncAuth, truncPrev := truncateAuthAndPrevEvents(refs, queryRes.LatestEvents)
diff --git a/federationapi/routing/join.go b/federationapi/routing/join.go
index 7edfccb29..0a7b23000 100644
--- a/federationapi/routing/join.go
+++ b/federationapi/routing/join.go
@@ -15,6 +15,7 @@
 package routing
 
 import (
+	"fmt"
 	"net/http"
 	"time"
 
@@ -34,6 +35,7 @@ func MakeJoin(
 	cfg *config.Dendrite,
 	query api.RoomserverQueryAPI,
 	roomID, userID string,
+	remoteVersions []gomatrixserverlib.RoomVersion,
 ) util.JSONResponse {
 	verReq := api.QueryRoomVersionForRoomRequest{RoomID: roomID}
 	verRes := api.QueryRoomVersionForRoomResponse{}
@@ -44,6 +46,27 @@ func MakeJoin(
 		}
 	}
 
+	// Check that the room that the remote side is trying to join is actually
+	// one of the room versions that they listed in their supported ?ver= in
+	// the make_join URL.
+	// https://matrix.org/docs/spec/server_server/r0.1.3#get-matrix-federation-v1-make-join-roomid-userid
+	remoteSupportsVersion := false
+	for _, v := range remoteVersions {
+		if v == verRes.RoomVersion {
+			remoteSupportsVersion = true
+			break
+		}
+	}
+	// If it isn't, stop trying to join the room.
+	if !remoteSupportsVersion {
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.UnsupportedRoomVersion(
+				fmt.Sprintf("Joining server does not support room version %s", verRes.RoomVersion),
+			),
+		}
+	}
+
 	_, domain, err := gomatrixserverlib.SplitID('@', userID)
 	if err != nil {
 		return util.JSONResponse{
@@ -140,7 +163,12 @@ func SendJoin(
 	if event.RoomID() != roomID {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: jsonerror.BadJSON("The room ID in the request path must match the room ID in the join event JSON"),
+			JSON: jsonerror.BadJSON(
+				fmt.Sprintf(
+					"The room ID in the request path (%q) must match the room ID in the join event JSON (%q)",
+					roomID, event.RoomID(),
+				),
+			),
 		}
 	}
 
@@ -148,7 +176,12 @@ func SendJoin(
 	if event.EventID() != eventID {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: jsonerror.BadJSON("The event ID in the request path must match the event ID in the join event JSON"),
+			JSON: jsonerror.BadJSON(
+				fmt.Sprintf(
+					"The event ID in the request path (%q) must match the event ID in the join event JSON (%q)",
+					eventID, event.EventID(),
+				),
+			),
 		}
 	}
 
diff --git a/federationapi/routing/routing.go b/federationapi/routing/routing.go
index a2b9dc210..83bac5550 100644
--- a/federationapi/routing/routing.go
+++ b/federationapi/routing/routing.go
@@ -198,7 +198,7 @@ func Setup(
 		},
 	)).Methods(http.MethodGet)
 
-	v1fedmux.Handle("/make_join/{roomID}/{userID}", common.MakeFedAPI(
+	v1fedmux.Handle("/make_join/{roomID}/{eventID}", common.MakeFedAPI(
 		"federation_make_join", cfg.Matrix.ServerName, keys,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest) util.JSONResponse {
 			vars, err := common.URLDecodeMapValues(mux.Vars(httpReq))
@@ -206,14 +206,28 @@ func Setup(
 				return util.ErrorResponse(err)
 			}
 			roomID := vars["roomID"]
-			userID := vars["userID"]
+			eventID := vars["eventID"]
+			queryVars := httpReq.URL.Query()
+			remoteVersions := []gomatrixserverlib.RoomVersion{}
+			if vers, ok := queryVars["ver"]; ok {
+				// The remote side supplied a ?=ver so use that to build up the list
+				// of supported room versions
+				for _, v := range vers {
+					remoteVersions = append(remoteVersions, gomatrixserverlib.RoomVersion(v))
+				}
+			} else {
+				// The remote side didn't supply a ?ver= so just assume that they only
+				// support room version 1, as per the spec
+				// https://matrix.org/docs/spec/server_server/r0.1.3#get-matrix-federation-v1-make-join-roomid-userid
+				remoteVersions = append(remoteVersions, gomatrixserverlib.RoomVersionV1)
+			}
 			return MakeJoin(
-				httpReq, request, cfg, query, roomID, userID,
+				httpReq, request, cfg, query, roomID, eventID, remoteVersions,
 			)
 		},
 	)).Methods(http.MethodGet)
 
-	v2fedmux.Handle("/send_join/{roomID}/{userID}", common.MakeFedAPI(
+	v2fedmux.Handle("/send_join/{roomID}/{eventID}", common.MakeFedAPI(
 		"federation_send_join", cfg.Matrix.ServerName, keys,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest) util.JSONResponse {
 			vars, err := common.URLDecodeMapValues(mux.Vars(httpReq))
@@ -221,14 +235,14 @@ func Setup(
 				return util.ErrorResponse(err)
 			}
 			roomID := vars["roomID"]
-			userID := vars["userID"]
+			eventID := vars["eventID"]
 			return SendJoin(
-				httpReq, request, cfg, query, producer, keys, roomID, userID,
+				httpReq, request, cfg, query, producer, keys, roomID, eventID,
 			)
 		},
 	)).Methods(http.MethodPut)
 
-	v1fedmux.Handle("/make_leave/{roomID}/{userID}", common.MakeFedAPI(
+	v1fedmux.Handle("/make_leave/{roomID}/{eventID}", common.MakeFedAPI(
 		"federation_make_leave", cfg.Matrix.ServerName, keys,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest) util.JSONResponse {
 			vars, err := common.URLDecodeMapValues(mux.Vars(httpReq))
@@ -236,14 +250,14 @@ func Setup(
 				return util.ErrorResponse(err)
 			}
 			roomID := vars["roomID"]
-			userID := vars["userID"]
+			eventID := vars["eventID"]
 			return MakeLeave(
-				httpReq, request, cfg, query, roomID, userID,
+				httpReq, request, cfg, query, roomID, eventID,
 			)
 		},
 	)).Methods(http.MethodGet)
 
-	v2fedmux.Handle("/send_leave/{roomID}/{userID}", common.MakeFedAPI(
+	v2fedmux.Handle("/send_leave/{roomID}/{eventID}", common.MakeFedAPI(
 		"federation_send_leave", cfg.Matrix.ServerName, keys,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest) util.JSONResponse {
 			vars, err := common.URLDecodeMapValues(mux.Vars(httpReq))
@@ -251,9 +265,9 @@ func Setup(
 				return util.ErrorResponse(err)
 			}
 			roomID := vars["roomID"]
-			userID := vars["userID"]
+			eventID := vars["eventID"]
 			return SendLeave(
-				httpReq, request, cfg, producer, keys, roomID, userID,
+				httpReq, request, cfg, producer, keys, roomID, eventID,
 			)
 		},
 	)).Methods(http.MethodPut)
diff --git a/go.mod b/go.mod
index e31f011c3..4f5b0a78d 100644
--- a/go.mod
+++ b/go.mod
@@ -9,7 +9,7 @@ require (
 	github.com/matrix-org/go-http-js-libp2p v0.0.0-20200318135427-31631a9ef51f
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20200325174927-327088cdef10
 	github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20200402141635-4a6e1ade46f8
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20200406135443-bfe03fcbf050
 	github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1
 	github.com/matrix-org/util v0.0.0-20190711121626-527ce5ddefc7
 	github.com/mattn/go-sqlite3 v2.0.2+incompatible
diff --git a/go.sum b/go.sum
index e5bb027a3..e6b83bb75 100644
--- a/go.sum
+++ b/go.sum
@@ -132,6 +132,8 @@ github.com/matrix-org/gomatrixserverlib v0.0.0-20200124100636-0c2ec91d1df5 h1:km
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200124100636-0c2ec91d1df5/go.mod h1:FsKa2pWE/bpQql9H7U4boOPXFoJX/QcqaZZ6ijLkaZI=
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200402141635-4a6e1ade46f8 h1:VZ7xGklSuzU9geMekuxKO4FvUBUaPjP+8IkcwzQtqOI=
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200402141635-4a6e1ade46f8/go.mod h1:FsKa2pWE/bpQql9H7U4boOPXFoJX/QcqaZZ6ijLkaZI=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200406135443-bfe03fcbf050 h1:SzSf5GN1ikjGSTEYdhpEUQubqIyH28vZIjYorzdU4Gc=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200406135443-bfe03fcbf050/go.mod h1:FsKa2pWE/bpQql9H7U4boOPXFoJX/QcqaZZ6ijLkaZI=
 github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1 h1:osLoFdOy+ChQqVUn2PeTDETFftVkl4w9t/OW18g3lnk=
 github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1/go.mod h1:cXoYQIENbdWIQHt1SyCo6Bl3C3raHwJ0wgVrXHSqf+A=
 github.com/matrix-org/util v0.0.0-20171127121716-2e2df66af2f5 h1:W7l5CP4V7wPyPb4tYE11dbmeAOwtFQBTW0rf4OonOS8=
diff --git a/roomserver/query/query.go b/roomserver/query/query.go
index ccd362774..7e05fe36f 100644
--- a/roomserver/query/query.go
+++ b/roomserver/query/query.go
@@ -132,7 +132,7 @@ func (r *RoomserverQueryAPI) QueryLatestEventsAndState(
 		return err
 	}
 
-	// Look up the currrent state for the requested tuples.
+	// Look up the current state for the requested tuples.
 	stateEntries, err := roomState.LoadStateAtSnapshotForStringTuples(
 		ctx, currentStateSnapshotNID, request.StateToFetch,
 	)
diff --git a/roomserver/version/version.go b/roomserver/version/version.go
index e60b5ef7a..f2a67e74d 100644
--- a/roomserver/version/version.go
+++ b/roomserver/version/version.go
@@ -59,7 +59,7 @@ var roomVersions = map[gomatrixserverlib.RoomVersion]RoomVersionDescription{
 // DefaultRoomVersion contains the room version that will, by
 // default, be used to create new rooms on this server.
 func DefaultRoomVersion() gomatrixserverlib.RoomVersion {
-	return gomatrixserverlib.RoomVersionV2
+	return gomatrixserverlib.RoomVersionV4
 }
 
 // RoomVersions returns a map of all known room versions to this
diff --git a/sytest-whitelist b/sytest-whitelist
index 8a1d54cec..44ff52c20 100644
--- a/sytest-whitelist
+++ b/sytest-whitelist
@@ -242,3 +242,5 @@ Remote user can backfill in a room with version 4
 # We don't support ignores yet, so ignore this for now - ha ha.
 # Ignore invite in incremental sync
 Outbound federation can send invites via v2 API
+User can invite local user to room with version 3
+User can invite local user to room with version 4