diff --git a/src/client_server/capabilities.rs b/src/client_server/capabilities.rs
index 8740928..65c8879 100644
--- a/src/client_server/capabilities.rs
+++ b/src/client_server/capabilities.rs
@@ -23,6 +23,7 @@ pub async fn get_capabilities_route(
     _body: Ruma<get_capabilities::Request>,
 ) -> ConduitResult<get_capabilities::Response> {
     let mut available = BTreeMap::new();
+    available.insert(RoomVersionId::Version5, RoomVersionStability::Stable);
     available.insert(RoomVersionId::Version6, RoomVersionStability::Stable);
 
     let mut capabilities = Capabilities::new();
diff --git a/src/client_server/membership.rs b/src/client_server/membership.rs
index e17a4d7..52bb18c 100644
--- a/src/client_server/membership.rs
+++ b/src/client_server/membership.rs
@@ -511,7 +511,7 @@ async fn join_room_by_id_helper(
                     federation::membership::create_join_event_template::v1::Request {
                         room_id,
                         user_id: sender_user,
-                        ver: &[RoomVersionId::Version6],
+                        ver: &[RoomVersionId::Version5, RoomVersionId::Version6],
                     },
                 )
                 .await;
@@ -526,7 +526,12 @@ async fn join_room_by_id_helper(
         let (make_join_response, remote_server) = make_join_response_and_server?;
 
         let room_version = match make_join_response.room_version {
-            Some(room_version) if room_version == RoomVersionId::Version6 => room_version,
+            Some(room_version)
+                if room_version == RoomVersionId::Version5
+                    || room_version == RoomVersionId::Version6 =>
+            {
+                room_version
+            }
             _ => return Err(Error::BadServerResponse("Room version is not supported")),
         };
 
@@ -940,7 +945,7 @@ pub async fn invite_helper<'a>(
                 create_invite::v2::Request {
                     room_id: room_id.clone(),
                     event_id: ruma::event_id!("$receivingservershouldsetthis"),
-                    room_version: RoomVersionId::Version6,
+                    room_version: room_version_id,
                     event: PduEvent::convert_to_outgoing_federation_event(pdu_json),
                     invite_room_state,
                 },
diff --git a/src/client_server/room.rs b/src/client_server/room.rs
index 6e27130..1d41fd8 100644
--- a/src/client_server/room.rs
+++ b/src/client_server/room.rs
@@ -346,7 +346,10 @@ pub async fn upgrade_room_route(
 ) -> ConduitResult<upgrade_room::Response> {
     let sender_user = body.sender_user.as_ref().expect("user is authenticated");
 
-    if !matches!(body.new_version, RoomVersionId::Version6) {
+    if !matches!(
+        body.new_version,
+        RoomVersionId::Version5 | RoomVersionId::Version6
+    ) {
         return Err(Error::BadRequest(
             ErrorKind::UnsupportedRoomVersion,
             "This server does not support that room version.",
diff --git a/src/database/rooms.rs b/src/database/rooms.rs
index aad691b..f0ec683 100644
--- a/src/database/rooms.rs
+++ b/src/database/rooms.rs
@@ -1954,7 +1954,11 @@ impl Rooms {
         let (make_leave_response, remote_server) = make_leave_response_and_server?;
 
         let room_version_id = match make_leave_response.room_version {
-            Some(id @ RoomVersionId::Version6) => id,
+            Some(version)
+                if version == RoomVersionId::Version5 || version == RoomVersionId::Version6 =>
+            {
+                version
+            }
             _ => return Err(Error::BadServerResponse("Room version is not supported")),
         };
 
diff --git a/src/pdu.rs b/src/pdu.rs
index a72f04d..c449eb8 100644
--- a/src/pdu.rs
+++ b/src/pdu.rs
@@ -328,6 +328,7 @@ pub(crate) fn gen_event_id_canonical_json(
 
     let event_id = EventId::try_from(&*format!(
         "${}",
+        // Anything higher than version3 behaves the same
         ruma::signatures::reference_hash(&value, &RoomVersionId::Version6)
             .expect("ruma can calculate reference hashes")
     ))
diff --git a/src/server_server.rs b/src/server_server.rs
index f666188..f725dce 100644
--- a/src/server_server.rs
+++ b/src/server_server.rs
@@ -1967,15 +1967,6 @@ pub fn create_join_event_template_route(
         ));
     }
 
-    if !body.ver.contains(&RoomVersionId::Version6) {
-        return Err(Error::BadRequest(
-            ErrorKind::IncompatibleRoomVersion {
-                room_version: RoomVersionId::Version6,
-            },
-            "Room version not supported.",
-        ));
-    }
-
     let prev_events = db
         .rooms
         .get_pdu_leaves(&body.room_id)?
@@ -2006,12 +1997,19 @@ pub fn create_join_event_template_route(
     };
 
     // If there was no create event yet, assume we are creating a version 6 room right now
-    let room_version = RoomVersion::new(
-        &create_event_content.map_or(RoomVersionId::Version6, |create_event| {
-            create_event.room_version
-        }),
-    )
-    .expect("room version is supported");
+    let room_version_id = create_event_content.map_or(RoomVersionId::Version6, |create_event| {
+        create_event.room_version
+    });
+    let room_version = RoomVersion::new(&room_version_id).expect("room version is supported");
+
+    if !body.ver.contains(&room_version_id) {
+        return Err(Error::BadRequest(
+            ErrorKind::IncompatibleRoomVersion {
+                room_version: room_version_id,
+            },
+            "Room version not supported.",
+        ));
+    }
 
     let content = serde_json::to_value(MemberEventContent {
         avatar_url: None,
@@ -2108,7 +2106,7 @@ pub fn create_join_event_template_route(
     );
 
     Ok(create_join_event_template::v1::Response {
-        room_version: Some(RoomVersionId::Version6),
+        room_version: Some(room_version_id),
         event: serde_json::from_value::<Raw<_>>(
             serde_json::to_value(pdu_json).expect("CanonicalJson is valid serde_json::Value"),
         )
@@ -2238,7 +2236,8 @@ pub async fn create_invite_route(
         return Err(Error::bad_config("Federation is disabled."));
     }
 
-    if body.room_version < RoomVersionId::Version6 {
+    if body.room_version != RoomVersionId::Version5 && body.room_version != RoomVersionId::Version6
+    {
         return Err(Error::BadRequest(
             ErrorKind::IncompatibleRoomVersion {
                 room_version: body.room_version.clone(),