diff --git a/lib/db/leveldb_test.go b/lib/db/leveldb_test.go
index 5dd58e0a..3b953b03 100644
--- a/lib/db/leveldb_test.go
+++ b/lib/db/leveldb_test.go
@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"testing"
 
+	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/protocol"
 )
 
@@ -152,3 +153,74 @@ func TestDropIndexIDs(t *testing.T) {
 		t.Fatal("fail remote 4")
 	}
 }
+
+func TestInvalidFiles(t *testing.T) {
+	ldb, err := openJSONS("testdata/v0.14.48-ignoredfiles.db.jsons")
+	if err != nil {
+		t.Fatal(err)
+	}
+	db := newDBInstance(ldb, "<memory>")
+	fs := NewFileSet("test", fs.NewFilesystem(fs.FilesystemTypeBasic, "."), db)
+
+	// The contents of the database are like this:
+	//
+	// 	fs := NewFileSet("test", fs.NewFilesystem(fs.FilesystemTypeBasic, "."), db)
+	// 	fs.Update(protocol.LocalDeviceID, []protocol.FileInfo{
+	// 		{ // invalid (ignored) file
+	// 			Name:    "foo",
+	// 			Type:    protocol.FileInfoTypeFile,
+	// 			Invalid: true,
+	// 			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 1, Value: 1000}}},
+	// 		},
+	// 		{ // regular file
+	// 			Name:    "bar",
+	// 			Type:    protocol.FileInfoTypeFile,
+	// 			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 1, Value: 1001}}},
+	// 		},
+	// 	})
+	// 	fs.Update(protocol.DeviceID{42}, []protocol.FileInfo{
+	// 		{ // invalid file
+	// 			Name:    "baz",
+	// 			Type:    protocol.FileInfoTypeFile,
+	// 			Invalid: true,
+	// 			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 42, Value: 1000}}},
+	// 		},
+	// 		{ // regular file
+	// 			Name:    "quux",
+	// 			Type:    protocol.FileInfoTypeFile,
+	// 			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 42, Value: 1002}}},
+	// 		},
+	// 	})
+
+	fi, ok := fs.Get(protocol.LocalDeviceID, "foo")
+	if !ok {
+		t.Fatal("foo should exist")
+	}
+	if !fi.Invalid {
+		t.Error("foo should be invalid")
+	}
+
+	fi, ok = fs.Get(protocol.LocalDeviceID, "bar")
+	if !ok {
+		t.Fatal("bar should exist")
+	}
+	if fi.Invalid {
+		t.Error("bar should not be invalid")
+	}
+
+	fi, ok = fs.Get(protocol.DeviceID{42}, "baz")
+	if !ok {
+		t.Fatal("baz should exist")
+	}
+	if !fi.Invalid {
+		t.Error("baz should be invalid")
+	}
+
+	fi, ok = fs.Get(protocol.DeviceID{42}, "quux")
+	if !ok {
+		t.Fatal("quux should exist")
+	}
+	if fi.Invalid {
+		t.Error("quux should not be invalid")
+	}
+}
diff --git a/lib/db/testdata/v0.14.48-ignoredfiles.db.jsons b/lib/db/testdata/v0.14.48-ignoredfiles.db.jsons
new file mode 100644
index 00000000..0b335e34
--- /dev/null
+++ b/lib/db/testdata/v0.14.48-ignoredfiles.db.jsons
@@ -0,0 +1,15 @@
+{"k":"AAAAAAAAAAABYmFy","v":"CgNiYXJKBwoFCAEQ6QdQAg=="}
+{"k":"AAAAAAAAAAABZm9v","v":"CgNmb284AUoHCgUIARDoB1AB"}
+{"k":"AAAAAAAAAAACYmF6","v":"CgNiYXo4AUoHCgUIKhDoBw=="}
+{"k":"AAAAAAAAAAACcXV1eA==","v":"CgRxdXV4SgcKBQgqEOoH"}
+{"k":"AQAAAABiYXI=","v":"CisKBwoFCAEQ6QcSIP//////////////////////////////////////////"}
+{"k":"AQAAAABiYXo=","v":"Ci0KBwoFCCoQ6AcSICoAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGAE="}
+{"k":"AQAAAABmb28=","v":"Ci0KBwoFCAEQ6AcSIP//////////////////////////////////////////GAE="}
+{"k":"AQAAAABxdXV4","v":"CisKBwoFCCoQ6gcSICoAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"}
+{"k":"BgAAAAAAAAAA","v":"dGVzdA=="}
+{"k":"BwAAAAAAAAAA","v":""}
+{"k":"BwAAAAEAAAAA","v":"//////////////////////////////////////////8="}
+{"k":"BwAAAAIAAAAA","v":"KgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="}
+{"k":"CQAAAAA=","v":"CicIATACigEg//////////////////////////////////////////8KJwgCMAKKASD4+Pj4+Pj4+Pj4+Pj4+Pj4+Pj4+Pj4+Pj4+Pj4+Pj4+AolCAGKASAqAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABCoudnCuM+vlxU="}
+{"k":"CwAAAAAAAAAAAAAAAQ==","v":"AAAAAAAAAAABZm9v"}
+{"k":"CwAAAAAAAAAAAAAAAg==","v":"AAAAAAAAAAABYmFy"}
diff --git a/lib/db/util_test.go b/lib/db/util_test.go
new file mode 100644
index 00000000..8eb525ac
--- /dev/null
+++ b/lib/db/util_test.go
@@ -0,0 +1,94 @@
+// Copyright (C) 2018 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package db
+
+import (
+	"encoding/json"
+	"io"
+	"os"
+
+	"github.com/syncthing/syncthing/lib/fs"
+	"github.com/syncthing/syncthing/lib/protocol"
+	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// writeJSONS serializes the database to a JSON stream that can be checked
+// in to the repo and used for tests.
+func writeJSONS(w io.Writer, db *leveldb.DB) {
+	it := db.NewIterator(&util.Range{}, nil)
+	defer it.Release()
+	enc := json.NewEncoder(w)
+	for it.Next() {
+		enc.Encode(map[string][]byte{
+			"k": it.Key(),
+			"v": it.Value(),
+		})
+	}
+}
+
+// openJSONS reads a JSON stream file into a leveldb.DB
+func openJSONS(file string) (*leveldb.DB, error) {
+	fd, err := os.Open(file)
+	if err != nil {
+		return nil, err
+	}
+	dec := json.NewDecoder(fd)
+
+	db, _ := leveldb.Open(storage.NewMemStorage(), nil)
+
+	for {
+		var row map[string][]byte
+
+		err := dec.Decode(&row)
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+
+		db.Put(row["k"], row["v"], nil)
+	}
+
+	return db, nil
+}
+
+func generateIgnoredFilesDB() {
+	// This generates a database with files with invalid flags, local and
+	// remote, in the format used in 0.14.48.
+
+	db := OpenMemory()
+	fs := NewFileSet("test", fs.NewFilesystem(fs.FilesystemTypeBasic, "."), db)
+	fs.Update(protocol.LocalDeviceID, []protocol.FileInfo{
+		{ // invalid (ignored) file
+			Name:    "foo",
+			Type:    protocol.FileInfoTypeFile,
+			Invalid: true,
+			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 1, Value: 1000}}},
+		},
+		{ // regular file
+			Name:    "bar",
+			Type:    protocol.FileInfoTypeFile,
+			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 1, Value: 1001}}},
+		},
+	})
+	fs.Update(protocol.DeviceID{42}, []protocol.FileInfo{
+		{ // invalid file
+			Name:    "baz",
+			Type:    protocol.FileInfoTypeFile,
+			Invalid: true,
+			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 42, Value: 1000}}},
+		},
+		{ // regular file
+			Name:    "quux",
+			Type:    protocol.FileInfoTypeFile,
+			Version: protocol.Vector{Counters: []protocol.Counter{{ID: 42, Value: 1002}}},
+		},
+	})
+	writeJSONS(os.Stdout, db.DB)
+}