diff --git a/programs/wineboot/wineboot.c b/programs/wineboot/wineboot.c
index c05ce580298..76d9812a4bf 100644
--- a/programs/wineboot/wineboot.c
+++ b/programs/wineboot/wineboot.c
@@ -1498,20 +1498,23 @@ static void update_wineprefix( BOOL force )
             HWND hwnd = show_wait_window();
             for (;;)
             {
-                MSG msg;
-                DWORD res = MsgWaitForMultipleObjects( 1, &process, FALSE, INFINITE, QS_ALLINPUT );
-                if (res == WAIT_OBJECT_0)
+                if (process)
                 {
+                    MSG msg;
+                    DWORD res = MsgWaitForMultipleObjects( 1, &process, FALSE, INFINITE, QS_ALLINPUT );
+                    if (res != WAIT_OBJECT_0)
+                    {
+                        while (PeekMessageW( &msg, 0, 0, 0, PM_REMOVE )) DispatchMessageW( &msg );
+                        continue;
+                    }
                     CloseHandle( process );
-                    if (!machines[count]) break;
-                    if (HIWORD(machines[count]) & 4 /* native machine */)
-                        process = start_rundll32( inf_path, L"DefaultInstall", IMAGE_FILE_MACHINE_TARGET_HOST );
-                    else
-                        process = start_rundll32( inf_path, L"Wow64Install", LOWORD(machines[count]) );
-                    count++;
-                    if (!process) break;
                 }
-                else while (PeekMessageW( &msg, 0, 0, 0, PM_REMOVE )) DispatchMessageW( &msg );
+                if (!machines[count]) break;
+                if (HIWORD(machines[count]) & 4 /* native machine */)
+                    process = start_rundll32( inf_path, L"DefaultInstall", IMAGE_FILE_MACHINE_TARGET_HOST );
+                else
+                    process = start_rundll32( inf_path, L"Wow64Install", LOWORD(machines[count]) );
+                count++;
             }
             DestroyWindow( hwnd );
         }