diff --git a/td/mtproto/TcpTransport.cpp b/td/mtproto/TcpTransport.cpp
index bf09ea6e..dd1da5be 100644
--- a/td/mtproto/TcpTransport.cpp
+++ b/td/mtproto/TcpTransport.cpp
@@ -149,12 +149,12 @@ void ObfuscatedTransport::init(ChainBufferReader *input, ChainBufferWriter *outp
     if (as<uint8>(header.data()) == 0xef) {
       continue;
     }
-    auto first_int = as<uint32>(header.data());
+    uint32 first_int = as<uint32>(header.data());
     if (first_int == 0x44414548 || first_int == 0x54534f50 || first_int == 0x20544547 || first_int == 0x4954504f ||
         first_int == 0xdddddddd || first_int == 0xeeeeeeee) {
       continue;
     }
-    auto second_int = as<uint32>(header.data() + sizeof(uint32));
+    uint32 second_int = as<uint32>(header.data() + sizeof(uint32));
     if (second_int == 0) {
       continue;
     }
diff --git a/td/mtproto/Transport.cpp b/td/mtproto/Transport.cpp
index 58915142..5a460d7c 100644
--- a/td/mtproto/Transport.cpp
+++ b/td/mtproto/Transport.cpp
@@ -296,7 +296,7 @@ Result<Transport::ReadResult> Transport::read(MutableSlice message, const AuthKe
       return Status::Error(PSLICE() << "Invalid mtproto message: smaller than 4 bytes [size=" << message.size() << "]");
     }
 
-    auto code = as<int32>(message.begin());
+    int32 code = as<int32>(message.begin());
     if (code == 0) {
       return ReadResult::make_nop();
     } else if (code == -1 && message.size() >= 8) {
diff --git a/td/telegram/SecretChatActor.cpp b/td/telegram/SecretChatActor.cpp
index e971f38f..b0c225f3 100644
--- a/td/telegram/SecretChatActor.cpp
+++ b/td/telegram/SecretChatActor.cpp
@@ -865,7 +865,7 @@ Result<std::tuple<uint64, BufferSlice, int32>> SecretChatActor::decrypt(BufferSl
       UNREACHABLE();
   }
 
-  auto len = as<int32>(data.begin());
+  int32 len = as<int32>(data.begin());
   data = data.substr(4, len);
   if (!is_aligned_pointer<4>(data.data())) {
     return std::make_tuple(auth_key_id, BufferSlice(data), mtproto_version);
diff --git a/td/telegram/SecureStorage.cpp b/td/telegram/SecureStorage.cpp
index cc962156..6df6d5c6 100644
--- a/td/telegram/SecureStorage.cpp
+++ b/td/telegram/SecureStorage.cpp
@@ -184,7 +184,7 @@ Result<Secret> Secret::create(Slice secret) {
 
   UInt256 secret_sha256;
   sha256(secret, ::td::as_slice(secret_sha256));
-  auto hash = as<int64>(secret_sha256.raw);
+  int64 hash = as<int64>(secret_sha256.raw);
   return Secret{res, hash};
 }
 
diff --git a/td/telegram/files/FileDownloader.cpp b/td/telegram/files/FileDownloader.cpp
index 99ad9f74..b7dbbf8c 100644
--- a/td/telegram/files/FileDownloader.cpp
+++ b/td/telegram/files/FileDownloader.cpp
@@ -320,7 +320,7 @@ Result<size_t> FileDownloader::process_part(Part part, NetQueryPtr net_query) {
     offset =
         ((offset & 0xff) << 24) | ((offset & 0xff00) << 8) | ((offset & 0xff0000) >> 8) | ((offset & 0xff000000) >> 24);
     as<uint32>(iv.raw + 12) = offset;
-    auto key = as<UInt256>(cdn_encryption_key_.c_str());
+    UInt256 key = as<UInt256>(cdn_encryption_key_.c_str());
 
     AesCtrState ctr_state;
     ctr_state.init(key, iv);
diff --git a/tdutils/td/utils/as.h b/tdutils/td/utils/as.h
index cf8f17cb..9d2094d9 100644
--- a/tdutils/td/utils/as.h
+++ b/tdutils/td/utils/as.h
@@ -10,24 +10,31 @@
 
 namespace td {
 
+namespace detail {
+
 template <class T>
 class As {
  public:
-  As(void *ptr) : ptr_(ptr) {
+  explicit As(void *ptr) : ptr_(ptr) {
   }
+
+  As(const As &new_value) = delete;
+  As &operator=(const As &) = delete;
   As(As &&) = default;
-  As<T> &operator=(const As &new_value) && {
-    memcpy(ptr_, new_value.ptr_, sizeof(T));
+  As &operator=(As &&new_value) && {
+    std::memcpy(ptr_, new_value.ptr_, sizeof(T));
     return *this;
   }
-  As<T> &operator=(const T new_value) && {
-    memcpy(ptr_, &new_value, sizeof(T));
+  ~As() = default;
+
+  As &operator=(const T &new_value) && {
+    std::memcpy(ptr_, &new_value, sizeof(T));
     return *this;
   }
 
   operator T() const {
     T res;
-    memcpy(&res, ptr_, sizeof(T));
+    std::memcpy(&res, ptr_, sizeof(T));
     return res;
   }
 
@@ -38,12 +45,12 @@ class As {
 template <class T>
 class ConstAs {
  public:
-  ConstAs(const void *ptr) : ptr_(ptr) {
+  explicit ConstAs(const void *ptr) : ptr_(ptr) {
   }
 
   operator T() const {
     T res;
-    memcpy(&res, ptr_, sizeof(T));
+    std::memcpy(&res, ptr_, sizeof(T));
     return res;
   }
 
@@ -51,14 +58,16 @@ class ConstAs {
   const void *ptr_;
 };
 
+}  // namespace detail
+
 template <class ToT, class FromT>
-As<ToT> as(FromT *from) {
-  return As<ToT>(from);
+detail::As<ToT> as(FromT *from) {
+  return detail::As<ToT>(from);
 }
 
 template <class ToT, class FromT>
-const ConstAs<ToT> as(const FromT *from) {
-  return ConstAs<ToT>(from);
+const detail::ConstAs<ToT> as(const FromT *from) {
+  return detail::ConstAs<ToT>(from);
 }
 
 }  // namespace td