diff --git a/reactos/include/reactos/drivers/directx/dxeng.h b/reactos/include/reactos/drivers/directx/dxeng.h
index 05213c55474..e523859ad86 100644
--- a/reactos/include/reactos/drivers/directx/dxeng.h
+++ b/reactos/include/reactos/drivers/directx/dxeng.h
@@ -87,14 +87,15 @@ BOOLEAN DxEngCleanDC(HDC hdc);
 DWORD DxEngGetHdevData(HDEV, DXEGSHDEVDATA);
 BOOLEAN DxEngSetHdevData(HDEV, DXEGSHDEVDATA, DWORD);
 BOOLEAN DxEngIncDispUniq();
+BOOLEAN DxEngLockHdev(HDEV hdev);
+BOOLEAN DxEngUnlockHdev(HDEV hdev);
 
 /* prototypes are not done yet, I need gather all my notes
  * to make them correct
  */
 DWORD DxEngCreateMemoryDC(DWORD x1);
 DWORD DxEngScreenAccessCheck();
-DWORD DxEngLockHdev(DWORD x1);
-DWORD DxEngUnlockHdev(DWORD x1);
+
 DWORD DxEngReferenceHdev(DWORD x1);
 DWORD DxEngIsHdevLockedByCurrentThread(DWORD x1);
 DWORD DxEngUnreferenceHdev(DWORD x1);
diff --git a/reactos/subsystems/win32/win32k/ntddraw/dxeng.c b/reactos/subsystems/win32/win32k/ntddraw/dxeng.c
index c766274255a..a94ce96beff 100644
--- a/reactos/subsystems/win32/win32k/ntddraw/dxeng.c
+++ b/reactos/subsystems/win32/win32k/ntddraw/dxeng.c
@@ -465,6 +465,67 @@ DxEngIncDispUniq()
     return TRUE;
 }
 
+/*++
+* @name DxEngLockHdev
+* @implemented
+*
+* The function DxEngLockHdev lock the internal PDEV
+*
+* @param HDEV type
+* it is a pointer to win32k internal pdev struct known as PGDIDEVICE
+
+* @return
+* This function returns TRUE no matter what.
+*
+* @remarks.
+* none
+*
+*--*/
+BOOLEAN 
+DxEngLockHdev(HDEV hDev)
+{
+    PGDIDEVICE pPDev = (PGDIDEVICE)hDev;
+    PERESOURCE Resource = pPDev->hsemDevLock;
+
+    if (Resource)
+    {
+        KeEnterCriticalRegion();
+        ExAcquireResourceExclusiveLite( Resource , TRUE); // Lock monitor.
+    }
+    return TRUE;
+}
+
+/*++
+* @name DxEngUnlockHdev
+* @implemented
+*
+* The function DxEngUnlockHdev unlock the internal PDEV
+*
+* @param HDEV type
+* it is a pointer to win32k internal pdev struct known as PGDIDEVICE
+
+* @return
+* This function returns TRUE no matter what.
+*
+* @remarks.
+* none
+*
+*--*/
+BOOLEAN 
+DxEngUnlockHdev(HDEV hDev)
+{
+    PGDIDEVICE pPDev = (PGDIDEVICE)hDev;
+    PERESOURCE Resource = pPDev->hsemDevLock;
+
+    if (Resource)
+    {
+        ExReleaseResourceLite( Resource );
+        KeLeaveCriticalRegion();
+    }
+    return TRUE;
+}
+
+
 /************************************************************************/
 /* DxEngNUIsTermSrv                                                     */
 /************************************************************************/
@@ -532,23 +593,7 @@ DWORD DxEngScreenAccessCheck()
     return FALSE;
 }
 
-/************************************************************************/
-/* DxEngLockHdev                                                        */
-/************************************************************************/
-DWORD DxEngLockHdev(DWORD x1)
-{
-    UNIMPLEMENTED;
-    return FALSE;
-}
 
-/************************************************************************/
-/* DxEngUnlockHdev                                                      */
-/************************************************************************/
-DWORD DxEngUnlockHdev(DWORD x1)
-{
-    UNIMPLEMENTED;
-    return FALSE;
-}
 
 /************************************************************************/
 /* DxEngReferenceHdev                                                   */