diff --git a/tdutils/td/utils/port/detail/EventFdWindows.cpp b/tdutils/td/utils/port/detail/EventFdWindows.cpp
index 7b55b338..0542739d 100644
--- a/tdutils/td/utils/port/detail/EventFdWindows.cpp
+++ b/tdutils/td/utils/port/detail/EventFdWindows.cpp
@@ -16,7 +16,12 @@ namespace td {
 namespace detail {
 
 void EventFdWindows::init() {
-  event_ = NativeFd(CreateEventW(nullptr, true, false, nullptr));
+  auto handle = CreateEventW(nullptr, true, false, nullptr);
+  if (handle == nullptr) {
+    auto error = OS_ERROR("CreateEventW failed");
+    LOG(FATAL) << error;
+  }
+  event_ = NativeFd(handle);
 }
 
 bool EventFdWindows::empty() {
@@ -36,16 +41,25 @@ PollableFdInfo &EventFdWindows::get_poll_info() {
 }
 
 void EventFdWindows::release() {
-  SetEvent(event_.fd());
+  if (SetEvent(event_.fd()) == 0) {
+    auto error = OS_ERROR("SetEvent failed");
+    LOG(FATAL) << error;
+  }
 }
 
 void EventFdWindows::acquire() {
-  ResetEvent(event_.fd());
+  if (ResetEvent(event_.fd()) == 0) {
+    auto error = OS_ERROR("ResetEvent failed");
+    LOG(FATAL) << error;
+  }
 }
 
 void EventFdWindows::wait(int timeout_ms) {
   WaitForSingleObject(event_.fd(), timeout_ms);
-  ResetEvent(event_.fd());
+  if (ResetEvent(event_.fd()) == 0) {
+    auto error = OS_ERROR("ResetEvent failed");
+    LOG(FATAL) << error;
+  }
 }
 
 }  // namespace detail
diff --git a/tdutils/td/utils/port/detail/Iocp.cpp b/tdutils/td/utils/port/detail/Iocp.cpp
index f651d54e..9e3f2b5b 100644
--- a/tdutils/td/utils/port/detail/Iocp.cpp
+++ b/tdutils/td/utils/port/detail/Iocp.cpp
@@ -69,7 +69,7 @@ void Iocp::subscribe(const NativeFd &native_fd, Callback *callback) {
   CHECK(iocp_handle_);
   auto iocp_handle =
       CreateIoCompletionPort(native_fd.fd(), iocp_handle_.fd(), reinterpret_cast<ULONG_PTR>(callback), 0);
-  if (iocp_handle == INVALID_HANDLE_VALUE) {
+  if (iocp_handle == nullptr) {
     auto error = OS_ERROR("CreateIoCompletionPort");
     LOG(FATAL) << error;
   }
@@ -77,8 +77,11 @@ void Iocp::subscribe(const NativeFd &native_fd, Callback *callback) {
 }
 
 void Iocp::post(size_t size, Callback *callback, WSAOVERLAPPED *overlapped) {
-  PostQueuedCompletionStatus(iocp_handle_.fd(), DWORD(size), reinterpret_cast<ULONG_PTR>(callback),
-                             reinterpret_cast<OVERLAPPED *>(overlapped));
+  if (PostQueuedCompletionStatus(iocp_handle_.fd(), DWORD(size), reinterpret_cast<ULONG_PTR>(callback),
+                                 reinterpret_cast<OVERLAPPED *>(overlapped)) == 0) {
+    auto error = OS_ERROR("IOCP post failed");
+    LOG(FATAL) << error;
+  }
 }
 
 }  // namespace detail