diff --git a/src/test/fuzz/block.cpp b/src/test/fuzz/block.cpp
index 431248de4a7..4a97eca18a5 100644
--- a/src/test/fuzz/block.cpp
+++ b/src/test/fuzz/block.cpp
@@ -15,6 +15,7 @@
 #include <version.h>
 
 #include <cassert>
+#include <memory>
 #include <string>
 
 void initialize()
@@ -59,5 +60,7 @@ void test_one_input(const std::vector<uint8_t>& buffer)
     }
     (void)GetBlockWeight(block);
     (void)GetWitnessCommitmentIndex(block);
-    (void)RecursiveDynamicUsage(block);
+    const size_t raw_memory_size = RecursiveDynamicUsage(block);
+    const size_t raw_memory_size_as_shared_ptr = RecursiveDynamicUsage(std::make_shared<CBlock>(block));
+    assert(raw_memory_size_as_shared_ptr > raw_memory_size);
 }