diff --git a/dll/win32/kernel32/client/synch.c b/dll/win32/kernel32/client/synch.c
index f7df2f710a..a022e4c33b 100644
--- a/dll/win32/kernel32/client/synch.c
+++ b/dll/win32/kernel32/client/synch.c
@@ -802,7 +802,16 @@ WINAPI
 SleepEx(IN DWORD dwMilliseconds,
         IN BOOL bAlertable)
 {
+    /*
+     * This function is the optimized of the following code:
+     *
+     *     DWORD wait = WaitForSingleObjectEx(GetCurrentThread(), dwMilliseconds, bAlertable);
+     *     if (wait == WAIT_IO_COMPLETION)
+     *         return wait;
+     *     return 0;
+     */
     LARGE_INTEGER Time;
+    HANDLE hCurrentThread;
     PLARGE_INTEGER TimePtr;
     NTSTATUS errCode;
     RTL_CALLER_ALLOCATED_ACTIVATION_CONTEXT_STACK_FRAME ActCtx;
@@ -819,27 +828,29 @@ SleepEx(IN DWORD dwMilliseconds,
 
     /* Convert the timeout */
     TimePtr = BaseFormatTimeOut(&Time, dwMilliseconds);
-    if (!TimePtr)
-    {
-        /* Turn an infinite wait into a really long wait */
-        Time.LowPart = 0;
-        Time.HighPart = 0x80000000;
-        TimePtr = &Time;
-    }
 
-    /* Loop the delay while APCs are alerting us */
+    /* Get the current thread handle */
+    hCurrentThread = (HANDLE)NtCurrentThread();
+
+    /* Start wait loop */
     do
     {
-        /* Do the delay */
-        errCode = NtDelayExecution((BOOLEAN)bAlertable, TimePtr);
+        /* Do the wait */
+        errCode = NtWaitForSingleObject(hCurrentThread, (BOOLEAN)bAlertable, TimePtr);
+        if (!NT_SUCCESS(errCode))
+        {
+            /* The wait failed */
+            BaseSetLastNTError(errCode);
+            errCode = WAIT_FAILED;
+        }
     }
     while ((bAlertable) && (errCode == STATUS_ALERTED));
-    
+
     /* Cleanup the activation context */
     if (bAlertable) RtlDeactivateActivationContextUnsafeFast(&ActCtx);
 
     /* Return the correct code */
-    return (errCode == STATUS_USER_APC) ? WAIT_IO_COMPLETION : 0;
+    return (errCode == WAIT_IO_COMPLETION) ? errCode : 0;
 }
 
 /*