diff --git "a/win32ss/user/ntuser/msgqueue.c" "b/win32ss/user/ntuser/msgqueue.c"
index 7f308530749..35f43d2d482 100644
--- "a/win32ss/user/ntuser/msgqueue.c"
+++ "b/win32ss/user/ntuser/msgqueue.c"
@@ -245,8 +245,17 @@ UserGetKeyState(DWORD dwKey)
 static VOID
 UpdateKeyState(PUSER_MESSAGE_QUEUE MessageQueue, WORD wVk, BOOL bIsDown)
 {
+    static PUSER_MESSAGE_QUEUE SysMsgQue = NULL;
     TRACE("UpdateKeyState wVk: %u, bIsDown: %d\n", wVk, bIsDown);
 
+    if (!SysMsgQue)
+    {
+        /* The first time this functions is entered it will be
+         * with the System Message Queue. Save it for later. */
+        SysMsgQue = MessageQueue;
+        TRACE("Storing SysMsgQue '%p'.\n", MessageQueue);
+    }
+
     if (bIsDown)
     {
         /* If it's first key down event, xor lock bit */
@@ -257,7 +266,17 @@ UpdateKeyState(PUSER_MESSAGE_QUEUE MessageQueue, WORD wVk, BOOL bIsDown)
         MessageQueue->afKeyRecentDown[wVk / 8] |= (1 << (wVk % 8));
     }
     else
+    {
         SET_KEY_DOWN(MessageQueue->afKeyState, wVk, FALSE);
+        if (SysMsgQue && (MessageQueue != SysMsgQue) && (wVk == VK_SHIFT))
+        {
+            /* If this is the shift key up and not going to the
+             * System Message Queue, then send it to the saved
+             * System Message Queue. See CORE-18525. */
+            SET_KEY_DOWN(SysMsgQue->afKeyState, wVk, FALSE);
+            TRACE("SysMsgQue Fixing '%u'.\n", wVk);
+        }
+    }
 }
 
 /* update the input key state for a keyboard message */