diff --git a/go.mod b/go.mod
index b04c503bd..30e3c97bd 100644
--- a/go.mod
+++ b/go.mod
@@ -31,7 +31,7 @@ require (
 	github.com/matrix-org/go-http-js-libp2p v0.0.0-20200518170932-783164aeeda4
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20210709140738-b0d1ba599a6d
 	github.com/matrix-org/gomatrix v0.0.0-20210324163249-be2af5ef2e16
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20210722084509-b9eb787c3967
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20210722110442-5061d6986876
 	github.com/matrix-org/naffka v0.0.0-20210623111924-14ff508b58e0
 	github.com/matrix-org/pinecone v0.0.0-20210623102758-74f885644c1b
 	github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4
diff --git a/go.sum b/go.sum
index 72986d3d0..a090dbc33 100644
--- a/go.sum
+++ b/go.sum
@@ -1027,8 +1027,8 @@ github.com/matrix-org/go-sqlite3-js v0.0.0-20210709140738-b0d1ba599a6d/go.mod h1
 github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26/go.mod h1:3fxX6gUjWyI/2Bt7J1OLhpCzOfO/bB3AiX0cJtEKud0=
 github.com/matrix-org/gomatrix v0.0.0-20210324163249-be2af5ef2e16 h1:ZtO5uywdd5dLDCud4r0r55eP4j9FuUNpl60Gmntcop4=
 github.com/matrix-org/gomatrix v0.0.0-20210324163249-be2af5ef2e16/go.mod h1:/gBX06Kw0exX1HrwmoBibFA98yBk/jxKpGVeyQbff+s=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20210722084509-b9eb787c3967 h1:9NvlktHDcqMxbytdLd92rjfFtn59QwxqfV7i2BQSyHA=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20210722084509-b9eb787c3967/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20210722110442-5061d6986876 h1:6ypwCtgRLK0v/hGWvnd847+KTo9BSkP9N0A4qSniP4E=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20210722110442-5061d6986876/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
 github.com/matrix-org/naffka v0.0.0-20210623111924-14ff508b58e0 h1:HZCzy4oVzz55e+cOMiX/JtSF2UOY1evBl2raaE7ACcU=
 github.com/matrix-org/naffka v0.0.0-20210623111924-14ff508b58e0/go.mod h1:sjyPyRxKM5uw1nD2cJ6O2OxI6GOqyVBfNXqKjBZTBZE=
 github.com/matrix-org/pinecone v0.0.0-20210623102758-74f885644c1b h1:5X5vdWQ13xrNkJVqaJHPsrt7rKkMJH5iac0EtfOuxSg=
diff --git a/roomserver/internal/input/input_membership.go b/roomserver/internal/input/input_membership.go
index 44435bfd9..2511097d0 100644
--- a/roomserver/internal/input/input_membership.go
+++ b/roomserver/internal/input/input_membership.go
@@ -136,6 +136,8 @@ func (r *Inputer) updateMembership(
 		return updateToJoinMembership(mu, add, updates)
 	case gomatrixserverlib.Leave, gomatrixserverlib.Ban:
 		return updateToLeaveMembership(mu, add, newMembership, updates)
+	case gomatrixserverlib.Knock:
+		return updateToKnockMembership(mu, add, updates)
 	default:
 		panic(fmt.Errorf(
 			"input: membership %q is not one of the allowed values", newMembership,
@@ -220,6 +222,18 @@ func updateToLeaveMembership(
 	return updates, nil
 }
 
+func updateToKnockMembership(
+	mu *shared.MembershipUpdater, add *gomatrixserverlib.Event, updates []api.OutputEvent,
+) ([]api.OutputEvent, error) {
+	if mu.IsLeave() {
+		_, err := mu.SetToKnock(add)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return updates, nil
+}
+
 // membershipChanges pairs up the membership state changes.
 func membershipChanges(removed, added []types.StateEntry) []stateChange {
 	changes := pairUpChanges(removed, added)
diff --git a/roomserver/storage/shared/membership_updater.go b/roomserver/storage/shared/membership_updater.go
index 57f3a520a..f1f589a31 100644
--- a/roomserver/storage/shared/membership_updater.go
+++ b/roomserver/storage/shared/membership_updater.go
@@ -86,6 +86,11 @@ func (u *MembershipUpdater) IsLeave() bool {
 	return u.membership == tables.MembershipStateLeaveOrBan
 }
 
+// IsKnock implements types.MembershipUpdater
+func (u *MembershipUpdater) IsKnock() bool {
+	return u.membership == tables.MembershipStateKnock
+}
+
 // SetToInvite implements types.MembershipUpdater
 func (u *MembershipUpdater) SetToInvite(event gomatrixserverlib.Event) (bool, error) {
 	var inserted bool
@@ -180,3 +185,27 @@ func (u *MembershipUpdater) SetToLeave(senderUserID string, eventID string) ([]s
 	})
 	return inviteEventIDs, err
 }
+
+// SetToKnock implements types.MembershipUpdater
+func (u *MembershipUpdater) SetToKnock(event *gomatrixserverlib.Event) (bool, error) {
+	var inserted bool
+	err := u.d.Writer.Do(u.d.DB, u.txn, func(txn *sql.Tx) error {
+		senderUserNID, err := u.d.assignStateKeyNID(u.ctx, u.txn, event.Sender())
+		if err != nil {
+			return fmt.Errorf("u.d.AssignStateKeyNID: %w", err)
+		}
+		if u.membership != tables.MembershipStateKnock {
+			// Look up the NID of the new knock event
+			nIDs, err := u.d.EventNIDs(u.ctx, []string{event.EventID()})
+			if err != nil {
+				return fmt.Errorf("u.d.EventNIDs: %w", err)
+			}
+
+			if err = u.d.MembershipTable.UpdateMembership(u.ctx, u.txn, u.roomNID, u.targetUserNID, senderUserNID, tables.MembershipStateKnock, nIDs[event.EventID()], false); err != nil {
+				return fmt.Errorf("u.d.MembershipTable.UpdateMembership: %w", err)
+			}
+		}
+		return nil
+	})
+	return inserted, err
+}
diff --git a/roomserver/storage/tables/interface.go b/roomserver/storage/tables/interface.go
index f762cb712..8720d4007 100644
--- a/roomserver/storage/tables/interface.go
+++ b/roomserver/storage/tables/interface.go
@@ -120,6 +120,7 @@ const (
 	MembershipStateLeaveOrBan MembershipState = 1
 	MembershipStateInvite     MembershipState = 2
 	MembershipStateJoin       MembershipState = 3
+	MembershipStateKnock      MembershipState = 4
 )
 
 type Membership interface {