diff --git a/tests/10apidoc/09synced.pl b/tests/10apidoc/09synced.pl
index d20a85b37..a6099ad9a 100644
--- a/tests/10apidoc/09synced.pl
+++ b/tests/10apidoc/09synced.pl
@@ -205,7 +205,35 @@ sub await_sync_presence_contains {
 }
 
 
-push @EXPORT, qw( assert_room_members assert_state_room_members_matches );
+push @EXPORT, qw( assert_room_members assert_state_room_members_matches assert_room_state);
+
+# assert that the state body of a sync response is made up of the given state types.
+sub assert_room_state {
+   my ( $body, $room_id, $state_types ) = @_;
+
+   my $room = $body->{rooms}{join}{$room_id};
+   my $state = $room->{state}{events};
+
+   log_if_fail "Room", $room;
+
+   my $found_types = [];
+   foreach (@$state) {
+      push @$found_types, [ $_->{type}, $_->{state_key} ];
+   }
+
+   my $comp = sub {
+      my ($a, $b) = @_;
+      return ($a->[0] cmp $b->[0]) || ($a->[1] cmp $b->[1]);
+   };
+
+   $found_types = [ sort { &$comp($a, $b) } @$found_types ];
+   $state_types = [ sort { &$comp($a, $b) } @$state_types ];
+
+   log_if_fail "Found state types", $found_types;
+   log_if_fail "Desired state types", $state_types;
+
+   assert_deeply_eq($found_types, $state_types);
+}
 
 # assert that the given members are in the body of a sync response
 sub assert_room_members {
diff --git a/tests/31sync/15lazy-members.pl b/tests/31sync/15lazy-members.pl
index 9e1ffebbd..e0282e767 100644
--- a/tests/31sync/15lazy-members.pl
+++ b/tests/31sync/15lazy-members.pl
@@ -161,7 +161,14 @@
          matrix_sync( $alice, filter => $filter_id );
       })->then( sub {
          my ( $body ) = @_;
-         assert_room_members( $body, $room_id, [ $bob->user_id ]);
+         assert_room_state( $body, $room_id, [
+            [ 'm.room.create', '' ],
+            [ 'm.room.join_rules', '' ],
+            [ 'm.room.power_levels', '' ],
+            [ 'm.room.name', '' ],
+            [ 'm.room.history_visibility', '' ],
+            [ 'm.room.member', $bob->user_id ],
+         ]);
 
          matrix_send_room_text_message_synced( $charlie, $room_id,
             body => "Message from charlie",
@@ -170,7 +177,9 @@
          matrix_sync_again( $alice, filter => $filter_id );
       })->then( sub {
          my ( $body ) = @_;
-         assert_room_members( $body, $room_id, [ $charlie->user_id ]);
+         assert_room_state( $body, $room_id, [
+            [ 'm.room.member', $charlie->user_id ],
+         ]);
          Future->done(1);
       });
    };
@@ -258,7 +267,6 @@
       });
    };
 
-
 test "We don't send redundant membership state across incremental syncs by default",
    requires => [ local_user_fixtures( 3 ),
                  qw( can_sync ) ],