diff --git a/dlls/user32/winproc.c b/dlls/user32/winproc.c
index b1193773ed2..7d53269dc80 100644
--- a/dlls/user32/winproc.c
+++ b/dlls/user32/winproc.c
@@ -851,10 +851,7 @@ BOOL unpack_message( HWND hwnd, UINT message, WPARAM *wparam, LPARAM *lparam,
     case WM_MOVING:
     case CB_GETCOMBOBOXINFO:
     case WM_MDIGETACTIVE:
-        break;
     case WM_DEVICECHANGE:
-        if (!(*wparam & 0x8000)) return TRUE;
-        minsize = sizeof(DEV_BROADCAST_HDR);
         break;
     case WM_NOTIFY:
         /* WM_NOTIFY cannot be sent across processes (MSDN) */
diff --git a/dlls/win32u/message.c b/dlls/win32u/message.c
index 28a2b7d39cc..56a05ba7eac 100644
--- a/dlls/win32u/message.c
+++ b/dlls/win32u/message.c
@@ -876,6 +876,10 @@ static BOOL unpack_message( HWND hwnd, UINT message, WPARAM *wparam, LPARAM *lpa
         if (!*lparam) return TRUE;
         if (!get_buffer_space( buffer, sizeof(BOOL), size )) return FALSE;
         break;
+    case WM_DEVICECHANGE:
+        if (!(*wparam & 0x8000)) return TRUE;
+        minsize = sizeof(DEV_BROADCAST_HDR);
+        break;
     default:
         return TRUE;  /* message doesn't need any unpacking */
     }
@@ -1704,6 +1708,13 @@ size_t user_message_size( HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam,
     case WM_MDIGETACTIVE:
         if (lparam) size = sizeof(BOOL);
         break;
+    case WM_DEVICECHANGE:
+        if ((wparam & 0x8000) && lparam)
+        {
+            const DEV_BROADCAST_HDR *header = lparam_ptr;
+            size = header->dbch_size;
+        }
+        break;
     }
 
     return size;