diff --git a/src/test/fuzz/merkle.cpp b/src/test/fuzz/merkle.cpp
index 9ba461bbd6b..ad56b3ed004 100644
--- a/src/test/fuzz/merkle.cpp
+++ b/src/test/fuzz/merkle.cpp
@@ -52,7 +52,7 @@ FUZZ_TARGET(merkle)
 
     // Test ComputeMerkleRoot
     bool mutated = fuzzed_data_provider.ConsumeBool(); // output param, initial value shouldn't matter
-    const uint256 merkle_root = ComputeMerkleRoot(tx_hashes, &mutated);
+    const uint256 merkle_root = ComputeMerkleRoot(tx_hashes, fuzzed_data_provider.ConsumeBool() ? &mutated : nullptr);
 
     // Basic sanity checks for ComputeMerkleRoot
     if (tx_hashes.size() == 1) {