diff --git a/keyserver/internal/internal.go b/keyserver/internal/internal.go
index a0280dff..06fc4987 100644
--- a/keyserver/internal/internal.go
+++ b/keyserver/internal/internal.go
@@ -212,15 +212,13 @@ func (a *KeyInternalAPI) QueryDeviceMessages(ctx context.Context, req *api.Query
 		return nil
 	}
 	maxStreamID := int64(0)
+	// remove deleted devices
+	var result []api.DeviceMessage
 	for _, m := range msgs {
 		if m.StreamID > maxStreamID {
 			maxStreamID = m.StreamID
 		}
-	}
-	// remove deleted devices
-	var result []api.DeviceMessage
-	for _, m := range msgs {
-		if m.KeyJSON == nil {
+		if m.KeyJSON == nil || len(m.KeyJSON) == 0 {
 			continue
 		}
 		result = append(result, m)
diff --git a/keyserver/internal/internal_test.go b/keyserver/internal/internal_test.go
new file mode 100644
index 00000000..8a2c9c5d
--- /dev/null
+++ b/keyserver/internal/internal_test.go
@@ -0,0 +1,156 @@
+package internal_test
+
+import (
+	"context"
+	"reflect"
+	"testing"
+
+	"github.com/matrix-org/dendrite/keyserver/api"
+	"github.com/matrix-org/dendrite/keyserver/internal"
+	"github.com/matrix-org/dendrite/keyserver/storage"
+	"github.com/matrix-org/dendrite/setup/config"
+	"github.com/matrix-org/dendrite/test"
+)
+
+func mustCreateDatabase(t *testing.T, dbType test.DBType) (storage.Database, func()) {
+	t.Helper()
+	connStr, close := test.PrepareDBConnectionString(t, dbType)
+	db, err := storage.NewDatabase(nil, &config.DatabaseOptions{
+		ConnectionString: config.DataSource(connStr),
+	})
+	if err != nil {
+		t.Fatalf("failed to create new user db: %v", err)
+	}
+	return db, close
+}
+
+func Test_QueryDeviceMessages(t *testing.T) {
+	alice := test.NewUser(t)
+	type args struct {
+		req *api.QueryDeviceMessagesRequest
+		res *api.QueryDeviceMessagesResponse
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+		want    *api.QueryDeviceMessagesResponse
+	}{
+		{
+			name: "no existing keys",
+			args: args{
+				req: &api.QueryDeviceMessagesRequest{
+					UserID: "@doesNotExist:localhost",
+				},
+				res: &api.QueryDeviceMessagesResponse{},
+			},
+			want: &api.QueryDeviceMessagesResponse{},
+		},
+		{
+			name: "existing user returns devices",
+			args: args{
+				req: &api.QueryDeviceMessagesRequest{
+					UserID: alice.ID,
+				},
+				res: &api.QueryDeviceMessagesResponse{},
+			},
+			want: &api.QueryDeviceMessagesResponse{
+				StreamID: 6,
+				Devices: []api.DeviceMessage{
+					{
+						Type: api.TypeDeviceKeyUpdate, StreamID: 5, DeviceKeys: &api.DeviceKeys{
+							DeviceID:    "myDevice",
+							DisplayName: "first device",
+							UserID:      alice.ID,
+							KeyJSON:     []byte("ghi"),
+						},
+					},
+					{
+						Type: api.TypeDeviceKeyUpdate, StreamID: 6, DeviceKeys: &api.DeviceKeys{
+							DeviceID:    "mySecondDevice",
+							DisplayName: "second device",
+							UserID:      alice.ID,
+							KeyJSON:     []byte("jkl"),
+						}, // streamID 6
+					},
+				},
+			},
+		},
+	}
+
+	deviceMessages := []api.DeviceMessage{
+		{ // not the user we're looking for
+			Type: api.TypeDeviceKeyUpdate, DeviceKeys: &api.DeviceKeys{
+				UserID: "@doesNotExist:localhost",
+			},
+			// streamID 1 for this user
+		},
+		{ // empty keyJSON will be ignored
+			Type: api.TypeDeviceKeyUpdate, DeviceKeys: &api.DeviceKeys{
+				DeviceID: "myDevice",
+				UserID:   alice.ID,
+			}, // streamID 1
+		},
+		{
+			Type: api.TypeDeviceKeyUpdate, DeviceKeys: &api.DeviceKeys{
+				DeviceID: "myDevice",
+				UserID:   alice.ID,
+				KeyJSON:  []byte("abc"),
+			}, // streamID 2
+		},
+		{
+			Type: api.TypeDeviceKeyUpdate, DeviceKeys: &api.DeviceKeys{
+				DeviceID: "myDevice",
+				UserID:   alice.ID,
+				KeyJSON:  []byte("def"),
+			}, // streamID 3
+		},
+		{
+			Type: api.TypeDeviceKeyUpdate, DeviceKeys: &api.DeviceKeys{
+				DeviceID: "myDevice",
+				UserID:   alice.ID,
+				KeyJSON:  []byte(""),
+			}, // streamID 4
+		},
+		{
+			Type: api.TypeDeviceKeyUpdate, DeviceKeys: &api.DeviceKeys{
+				DeviceID:    "myDevice",
+				DisplayName: "first device",
+				UserID:      alice.ID,
+				KeyJSON:     []byte("ghi"),
+			}, // streamID 5
+		},
+		{
+			Type: api.TypeDeviceKeyUpdate, DeviceKeys: &api.DeviceKeys{
+				DeviceID:    "mySecondDevice",
+				UserID:      alice.ID,
+				KeyJSON:     []byte("jkl"),
+				DisplayName: "second device",
+			}, // streamID 6
+		},
+	}
+	ctx := context.Background()
+
+	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
+		db, closeDB := mustCreateDatabase(t, dbType)
+		defer closeDB()
+		if err := db.StoreLocalDeviceKeys(ctx, deviceMessages); err != nil {
+			t.Fatalf("failed to store local devicesKeys")
+		}
+
+		for _, tt := range tests {
+			t.Run(tt.name, func(t *testing.T) {
+				a := &internal.KeyInternalAPI{
+					DB: db,
+				}
+				if err := a.QueryDeviceMessages(ctx, tt.args.req, tt.args.res); (err != nil) != tt.wantErr {
+					t.Errorf("QueryDeviceMessages() error = %v, wantErr %v", err, tt.wantErr)
+				}
+				got := tt.args.res
+				if !reflect.DeepEqual(got, tt.want) {
+					t.Errorf("QueryDeviceMessages(): got:\n%+v, want:\n%+v", got, tt.want)
+				}
+			})
+		}
+	})
+}
diff --git a/keyserver/storage/postgres/device_keys_table.go b/keyserver/storage/postgres/device_keys_table.go
index ccd20cbd..2aa11c52 100644
--- a/keyserver/storage/postgres/device_keys_table.go
+++ b/keyserver/storage/postgres/device_keys_table.go
@@ -20,6 +20,7 @@ import (
 	"time"
 
 	"github.com/lib/pq"
+
 	"github.com/matrix-org/dendrite/internal"
 	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/keyserver/api"
@@ -204,20 +205,17 @@ func (s *deviceKeysStatements) SelectBatchDeviceKeys(ctx context.Context, userID
 		deviceIDMap[d] = true
 	}
 	var result []api.DeviceMessage
+	var displayName sql.NullString
 	for rows.Next() {
 		dk := api.DeviceMessage{
-			Type:       api.TypeDeviceKeyUpdate,
-			DeviceKeys: &api.DeviceKeys{},
+			Type: api.TypeDeviceKeyUpdate,
+			DeviceKeys: &api.DeviceKeys{
+				UserID: userID,
+			},
 		}
-		dk.UserID = userID
-		var keyJSON string
-		var streamID int64
-		var displayName sql.NullString
-		if err := rows.Scan(&dk.DeviceID, &keyJSON, &streamID, &displayName); err != nil {
+		if err := rows.Scan(&dk.DeviceID, &dk.KeyJSON, &dk.StreamID, &displayName); err != nil {
 			return nil, err
 		}
-		dk.KeyJSON = []byte(keyJSON)
-		dk.StreamID = streamID
 		if displayName.Valid {
 			dk.DisplayName = displayName.String
 		}
diff --git a/keyserver/storage/sqlite3/device_keys_table.go b/keyserver/storage/sqlite3/device_keys_table.go
index e77b49b3..73768da5 100644
--- a/keyserver/storage/sqlite3/device_keys_table.go
+++ b/keyserver/storage/sqlite3/device_keys_table.go
@@ -137,21 +137,17 @@ func (s *deviceKeysStatements) SelectBatchDeviceKeys(ctx context.Context, userID
 	}
 	defer internal.CloseAndLogIfError(ctx, rows, "selectBatchDeviceKeysStmt: rows.close() failed")
 	var result []api.DeviceMessage
+	var displayName sql.NullString
 	for rows.Next() {
 		dk := api.DeviceMessage{
-			Type:       api.TypeDeviceKeyUpdate,
-			DeviceKeys: &api.DeviceKeys{},
+			Type: api.TypeDeviceKeyUpdate,
+			DeviceKeys: &api.DeviceKeys{
+				UserID: userID,
+			},
 		}
-		dk.Type = api.TypeDeviceKeyUpdate
-		dk.UserID = userID
-		var keyJSON string
-		var streamID int64
-		var displayName sql.NullString
-		if err := rows.Scan(&dk.DeviceID, &keyJSON, &streamID, &displayName); err != nil {
+		if err := rows.Scan(&dk.DeviceID, &dk.KeyJSON, &dk.StreamID, &displayName); err != nil {
 			return nil, err
 		}
-		dk.KeyJSON = []byte(keyJSON)
-		dk.StreamID = streamID
 		if displayName.Valid {
 			dk.DisplayName = displayName.String
 		}