diff --git a/internal/api/stacks.go b/internal/api/stacks.go
index 5e3c42b..061ad5c 100644
--- a/internal/api/stacks.go
+++ b/internal/api/stacks.go
@@ -809,6 +809,10 @@ func checkImages(ctx context.Context, images []string) []imageCheck {
 // machineUpdates checks every image on this machine in one pass, so the container list can
 // be coloured and "what is behind?" answered without walking stack by stack.
 func (s *Server) machineUpdates(w http.ResponseWriter, r *http.Request) {
+	if dockerTool() == "" { // no Docker is an empty answer, not a failure
+		jsonOK(w, 200, map[string]any{"images": []imageCheck{}, "checked": 0, "stacks": map[string][]string{}})
+		return
+	}
 	ctx, cancel := context.WithTimeout(r.Context(), 10*time.Minute)
 	defer cancel()
 	stacks, err := s.findStacks(ctx)