diff --git a/src/coins.h b/src/coins.h
index 6e8643ccc25..5bf4c07e7af 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -733,6 +733,10 @@ public:
         CCoinsViewCache::Flush(reallocate_cache);
     }
 
+    //! Swapping the backend or writing through to it with Sync() is not supported while fetching.
+    void SetBackend(CCoinsView&) = delete;
+    void Sync() = delete;
+
     //! Verify that all parallel fetched input prevouts have been consumed.
     bool AllInputsConsumed() const noexcept { return m_input_tail == m_inputs.size(); }
 };
diff --git a/src/test/fuzz/coins_view.cpp b/src/test/fuzz/coins_view.cpp
index 5e1b08ade52..343eb993f0d 100644
--- a/src/test/fuzz/coins_view.cpp
+++ b/src/test/fuzz/coins_view.cpp
@@ -204,7 +204,7 @@ void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsViewCache& co
                 coins_view_cache.Uncache(random_out_point);
             },
             [&] {
-                if (overlay) return; // // CoinsViewOverlay::SetBackend() is never called in production code
+                if (overlay) return; // CoinsViewOverlay::SetBackend() is never called in production code
                 const bool use_original_backend{fuzzed_data_provider.ConsumeBool()};
                 if (use_original_backend && backend_coins_view != original_backend) {
                     // FRESH flags valid against the empty backend may be invalid
@@ -382,7 +382,7 @@ void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsViewCache& co
         // If HaveCoin on the backend is true, it must also be on the cache if the coin wasn't spent.
         std::optional<Coin> coin_in_backend;
         bool exists_using_have_coin_in_backend;
-        if (dynamic_cast<CoinsViewOverlay*>(&coins_view_cache)) {
+        if (overlay) {
             // PeekCoin does not mutate cacheCoins, so async workers can keep running.
             coin_in_backend = backend_coins_view->PeekCoin(random_out_point);
             exists_using_have_coin_in_backend = coin_in_backend.has_value();