diff --git a/ctypes_generation/definitions/functions/file.txt b/ctypes_generation/definitions/functions/file.txt
index 5ef391c..b74c02b 100644
--- a/ctypes_generation/definitions/functions/file.txt
+++ b/ctypes_generation/definitions/functions/file.txt
@@ -70,4 +70,21 @@ BOOL ReadDirectoryChangesExW(
   LPOVERLAPPED                            lpOverlapped,
   LPOVERLAPPED_COMPLETION_ROUTINE         lpCompletionRoutine,
   READ_DIRECTORY_NOTIFY_INFORMATION_CLASS ReadDirectoryNotifyInformationClass
+);
+
+BOOL LockFile(
+  [in] HANDLE hFile,
+  [in] DWORD  dwFileOffsetLow,
+  [in] DWORD  dwFileOffsetHigh,
+  [in] DWORD  nNumberOfBytesToLockLow,
+  [in] DWORD  nNumberOfBytesToLockHigh
+);
+
+BOOL LockFileEx(
+  [in]      HANDLE       hFile,
+  [in]      DWORD        dwFlags,
+            DWORD        dwReserved,
+  [in]      DWORD        nNumberOfBytesToLockLow,
+  [in]      DWORD        nNumberOfBytesToLockHigh,
+  [in, out] LPOVERLAPPED lpOverlapped
 );
\ No newline at end of file
diff --git a/ctypes_generation/definitions/structures/winstruct.txt b/ctypes_generation/definitions/structures/winstruct.txt
index dda5ea8..efb9932 100644
--- a/ctypes_generation/definitions/structures/winstruct.txt
+++ b/ctypes_generation/definitions/structures/winstruct.txt
@@ -1542,7 +1542,13 @@ typedef struct _OSVERSIONINFOEXW {
 typedef struct _OVERLAPPED {
   ULONG_PTR Internal;
   ULONG_PTR InternalHigh;
-  PVOID  Pointer;
+  union {
+    struct {
+      DWORD Offset;
+      DWORD OffsetHigh;
+    } _ANON_OVERLAPPED_DUMMYSTRUCTNAME;
+    PVOID Pointer;
+  } _ANON_OVERLAPPED_DUMMYUNIONNAME;
   HANDLE    hEvent;
 } OVERLAPPED, *LPOVERLAPPED;
 
diff --git a/windows/generated_def/meta.py b/windows/generated_def/meta.py
index c5e573d..0a562c5 100644
--- a/windows/generated_def/meta.py
+++ b/windows/generated_def/meta.py
@@ -14409,6 +14409,8 @@ functions = set(['AccessCheck',
      'LoadLibraryW',
      'LoadResource',
      'LocalFree',
+     'LockFile',
+     'LockFileEx',
      'LockResource',
      'LookupAccountNameA',
      'LookupAccountNameW',
diff --git a/windows/generated_def/winfuncs.py b/windows/generated_def/winfuncs.py
index bea99e1..c5b8e7a 100644
--- a/windows/generated_def/winfuncs.py
+++ b/windows/generated_def/winfuncs.py
@@ -1210,6 +1210,16 @@ ReadDirectoryChangesWParams = ((1, 'hDirectory'), (1, 'lpBuffer'), (1, 'nBufferL
 ReadDirectoryChangesExWPrototype = WINFUNCTYPE(BOOL, HANDLE, LPVOID, DWORD, BOOL, DWORD, LPDWORD, LPOVERLAPPED, LPOVERLAPPED_COMPLETION_ROUTINE, READ_DIRECTORY_NOTIFY_INFORMATION_CLASS)
 ReadDirectoryChangesExWParams = ((1, 'hDirectory'), (1, 'lpBuffer'), (1, 'nBufferLength'), (1, 'bWatchSubtree'), (1, 'dwNotifyFilter'), (1, 'lpBytesReturned'), (1, 'lpOverlapped'), (1, 'lpCompletionRoutine'), (1, 'ReadDirectoryNotifyInformationClass'))
 
+#def LockFile(hFile, dwFileOffsetLow, dwFileOffsetHigh, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh):
+#    return LockFile.ctypes_function(hFile, dwFileOffsetLow, dwFileOffsetHigh, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh)
+LockFilePrototype = WINFUNCTYPE(BOOL, HANDLE, DWORD, DWORD, DWORD, DWORD)
+LockFileParams = ((1, 'hFile'), (1, 'dwFileOffsetLow'), (1, 'dwFileOffsetHigh'), (1, 'nNumberOfBytesToLockLow'), (1, 'nNumberOfBytesToLockHigh'))
+
+#def LockFileEx(hFile, dwFlags, dwReserved, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh, lpOverlapped):
+#    return LockFileEx.ctypes_function(hFile, dwFlags, dwReserved, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh, lpOverlapped)
+LockFileExPrototype = WINFUNCTYPE(BOOL, HANDLE, DWORD, DWORD, DWORD, DWORD, LPOVERLAPPED)
+LockFileExParams = ((1, 'hFile'), (1, 'dwFlags'), (1, 'dwReserved'), (1, 'nNumberOfBytesToLockLow'), (1, 'nNumberOfBytesToLockHigh'), (1, 'lpOverlapped'))
+
 #def HeapAlloc(hHeap, dwFlags, dwBytes):
 #    return HeapAlloc.ctypes_function(hHeap, dwFlags, dwBytes)
 HeapAllocPrototype = WINFUNCTYPE(LPVOID, HANDLE, DWORD, SIZE_T)
diff --git a/windows/generated_def/winstructs.py b/windows/generated_def/winstructs.py
index beb195d..18317b5 100644
--- a/windows/generated_def/winstructs.py
+++ b/windows/generated_def/winstructs.py
@@ -5504,11 +5504,25 @@ OSVERSIONINFOEXW = _OSVERSIONINFOEXW
 POSVERSIONINFOEXW = POINTER(_OSVERSIONINFOEXW)
 RTL_OSVERSIONINFOEXW = _OSVERSIONINFOEXW
 
+class _ANON__ANON__OVERLAPPED_SUB_UNION_1_SUB_STRUCTURE_1(Structure):
+    _fields_ = [
+        ("Offset", DWORD),
+        ("OffsetHigh", DWORD),
+    ]
+
+class _ANON__OVERLAPPED_SUB_UNION_1(Union):
+    _anonymous_ = ("_ANON_OVERLAPPED_DUMMYSTRUCTNAME",)
+    _fields_ = [
+        ("_ANON_OVERLAPPED_DUMMYSTRUCTNAME", _ANON__ANON__OVERLAPPED_SUB_UNION_1_SUB_STRUCTURE_1),
+        ("Pointer", PVOID),
+    ]
+
 class _OVERLAPPED(Structure):
+    _anonymous_ = ("_ANON_OVERLAPPED_DUMMYUNIONNAME",)
     _fields_ = [
         ("Internal", ULONG_PTR),
         ("InternalHigh", ULONG_PTR),
-        ("Pointer", PVOID),
+        ("_ANON_OVERLAPPED_DUMMYUNIONNAME", _ANON__OVERLAPPED_SUB_UNION_1),
         ("hEvent", HANDLE),
     ]
 LPOVERLAPPED = POINTER(_OVERLAPPED)
diff --git a/windows/winproxy/apis/kernel32.py b/windows/winproxy/apis/kernel32.py
index 25aa3a0..3001c2f 100644
--- a/windows/winproxy/apis/kernel32.py
+++ b/windows/winproxy/apis/kernel32.py
@@ -580,7 +580,13 @@ def ReadDirectoryChangesW(hDirectory, lpBuffer, nBufferLength, bWatchSubtree, dw
 def ReadDirectoryChangesExW(hDirectory, lpBuffer, nBufferLength, bWatchSubtree, dwNotifyFilter, lpBytesReturned, lpOverlapped, lpCompletionRoutine, ReadDirectoryNotifyInformationClass):
     return ReadDirectoryChangesExW.ctypes_function(hDirectory, lpBuffer, nBufferLength, bWatchSubtree, dwNotifyFilter, lpBytesReturned, lpOverlapped, lpCompletionRoutine, ReadDirectoryNotifyInformationClass)
 
+@Kernel32Proxy()
+def LockFile(hFile, dwFileOffsetLow, dwFileOffsetHigh, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh):
+    return LockFile.ctypes_function(hFile, dwFileOffsetLow, dwFileOffsetHigh, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh)
 
+@Kernel32Proxy()
+def LockFileEx(hFile, dwFlags, dwReserved, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh, lpOverlapped):
+    return LockFileEx.ctypes_function(hFile, dwFlags, dwReserved, nNumberOfBytesToLockLow, nNumberOfBytesToLockHigh, lpOverlapped)
 
 ## Tlhelp (snapshoot)
 
diff --git a/windows/winproxy/apis/netapi32.py b/windows/winproxy/apis/netapi32.py
index 516e015..fdbc16a 100644
--- a/windows/winproxy/apis/netapi32.py
+++ b/windows/winproxy/apis/netapi32.py
@@ -2,11 +2,11 @@ import ctypes
 import windows.generated_def as gdef
 
 from ..apiproxy import ApiProxy, NeededParameter
-from ..error import succeed_on_zero
+from ..error import result_is_error_code
 
 class NetApi32Proxy(ApiProxy):
     APIDLL = "netapi32"
-    default_error_check = staticmethod(succeed_on_zero)
+    default_error_check = staticmethod(result_is_error_code)
 
 
 @NetApi32Proxy()