diff --git a/td/telegram/files/FileDb.cpp b/td/telegram/files/FileDb.cpp
index a7d028df..f976f38e 100644
--- a/td/telegram/files/FileDb.cpp
+++ b/td/telegram/files/FileDb.cpp
@@ -306,7 +306,7 @@ Status fix_file_remote_location_key_bug(SqliteDb &db) {
     auto remote_str = PSTRING() << key.substr(4, 4) << Slice("\0\0\0\0") << key.substr(8);
     FullRemoteFileLocation remote;
     if (unserialize(remote, remote_str).is_ok()) {
-      kv.set(as_key(remote), value);
+      kv.set(FileDbInterface::as_key(remote), value);
     }
     LOG(DEBUG) << "ERASE " << format::as_hex_dump<4>(Slice(key));
     kv.erase(key);
diff --git a/td/telegram/files/FileDb.h b/td/telegram/files/FileDb.h
index 8b7927a7..0fd04e7b 100644
--- a/td/telegram/files/FileDb.h
+++ b/td/telegram/files/FileDb.h
@@ -11,8 +11,10 @@
 
 #include "td/actor/PromiseFuture.h"
 
+#include "td/utils/buffer.h"
 #include "td/utils/logging.h"
 #include "td/utils/Status.h"
+#include "td/utils/tl_storers.h"
 
 #include <memory>
 
@@ -41,9 +43,25 @@ class FileDbInterface {
 
   // thread safe
   virtual void close(Promise<> promise) = 0;
+
+  template <class LocationT>
+  static string as_key(const LocationT &object) {
+    TlStorerCalcLength calc_length;
+    calc_length.store_int(0);
+    object.as_key().store(calc_length);
+
+    BufferSlice key_buffer{calc_length.get_length()};
+    auto key = key_buffer.as_slice();
+    TlStorerUnsafe storer(key.ubegin());
+    storer.store_int(LocationT::KEY_MAGIC);
+    object.as_key().store(storer);
+    CHECK(storer.get_buf() == key.uend());
+    return key.str();
+  }
+
   template <class LocationT>
   void get_file_data(const LocationT &location, Promise<FileData> promise) {
-    get_file_data(as_key(location), std::move(promise));
+    get_file_data_impl(as_key(location), std::move(promise));
   }
 
   template <class LocationT>
diff --git a/td/telegram/files/FileLocation.h b/td/telegram/files/FileLocation.h
index 415cb668..34b2a5c8 100644
--- a/td/telegram/files/FileLocation.h
+++ b/td/telegram/files/FileLocation.h
@@ -22,7 +22,6 @@
 #include "td/utils/Slice.h"
 #include "td/utils/StringBuilder.h"
 #include "td/utils/tl_helpers.h"
-#include "td/utils/tl_storers.h"
 #include "td/utils/Variant.h"
 
 #include <tuple>
@@ -1306,19 +1305,4 @@ inline StringBuilder &operator<<(StringBuilder &sb, const FileData &file_data) {
   return sb << "]";
 }
 
-template <class T>
-string as_key(const T &object) {
-  TlStorerCalcLength calc_length;
-  calc_length.store_int(0);
-  object.as_key().store(calc_length);
-
-  BufferSlice key_buffer{calc_length.get_length()};
-  auto key = key_buffer.as_slice();
-  TlStorerUnsafe storer(key.ubegin());
-  storer.store_int(T::KEY_MAGIC);
-  object.as_key().store(storer);
-  CHECK(storer.get_buf() == key.uend());
-  return key.str();
-}
-
 }  // namespace td