diff --git a/repos/ports/src/virtualbox6/include/fb.h b/repos/ports/src/virtualbox6/include/fb.h
index 7847697225..b154161fcb 100644
--- a/repos/ports/src/virtualbox6/include/fb.h
+++ b/repos/ports/src/virtualbox6/include/fb.h
@@ -100,7 +100,7 @@ class Genodefb :
 			_display(display)
 		{
 			int rc = RTCritSectInit(&_fb_lock);
-			Assert(rc == VINF_SUCCESS);
+			Assert(rc == VINF_SUCCESS); (void)rc;
 		}
 
 		virtual ~Genodefb() { }
diff --git a/repos/ports/src/virtualbox6/main.cc b/repos/ports/src/virtualbox6/main.cc
index 169a771792..0bbd2cd2df 100644
--- a/repos/ports/src/virtualbox6/main.cc
+++ b/repos/ports/src/virtualbox6/main.cc
@@ -414,7 +414,7 @@ void Main::_handle_fb_mode()
 		_gui_connections.for_each([&] (Gui::Connection &gui) {
 			IFramebuffer *pFramebuffer = NULL;
 			HRESULT rc = _idisplay->QueryFramebuffer(0, &pFramebuffer);
-			Assert(SUCCEEDED(rc) && pFramebuffer);
+			Assert(SUCCEEDED(rc) && pFramebuffer); (void)rc;
 
 			Genodefb *fb = dynamic_cast<Genodefb *>(pFramebuffer);