diff --git a/src/test/fuzz/crypto_chacha20.cpp b/src/test/fuzz/crypto_chacha20.cpp
index afe9324949..50c77bf699 100644
--- a/src/test/fuzz/crypto_chacha20.cpp
+++ b/src/test/fuzz/crypto_chacha20.cpp
@@ -17,15 +17,15 @@ FUZZ_TARGET(crypto_chacha20)
 {
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
 
-    const std::vector<unsigned char> key = ConsumeFixedLengthByteVector(fuzzed_data_provider, 32);
-    ChaCha20 chacha20{MakeByteSpan(key)};
+    const auto key = ConsumeFixedLengthByteVector<std::byte>(fuzzed_data_provider, ChaCha20::KEYLEN);
+    ChaCha20 chacha20{key};
 
     LIMITED_WHILE(fuzzed_data_provider.ConsumeBool(), 10000) {
         CallOneOf(
             fuzzed_data_provider,
             [&] {
-                std::vector<unsigned char> key = ConsumeFixedLengthByteVector(fuzzed_data_provider, 32);
-                chacha20.SetKey(MakeByteSpan(key));
+                auto key = ConsumeFixedLengthByteVector<std::byte>(fuzzed_data_provider, ChaCha20::KEYLEN);
+                chacha20.SetKey(key);
             },
             [&] {
                 chacha20.Seek(
@@ -39,9 +39,9 @@ FUZZ_TARGET(crypto_chacha20)
                 chacha20.Keystream(MakeWritableByteSpan(output));
             },
             [&] {
-                std::vector<uint8_t> output(fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
-                const std::vector<uint8_t> input = ConsumeFixedLengthByteVector(fuzzed_data_provider, output.size());
-                chacha20.Crypt(MakeByteSpan(input), MakeWritableByteSpan(output));
+                std::vector<std::byte> output(fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+                const auto input = ConsumeFixedLengthByteVector<std::byte>(fuzzed_data_provider, output.size());
+                chacha20.Crypt(input, output);
             });
     }
 }
@@ -60,8 +60,7 @@ template<bool UseCrypt>
 void ChaCha20SplitFuzz(FuzzedDataProvider& provider)
 {
     // Determine key, iv, start position, length.
-    auto key_bytes = provider.ConsumeBytes<std::byte>(ChaCha20::KEYLEN);
-    key_bytes.resize(ChaCha20::KEYLEN);
+    auto key_bytes = ConsumeFixedLengthByteVector<std::byte>(provider, ChaCha20::KEYLEN);
     uint64_t iv = provider.ConsumeIntegral<uint64_t>();
     uint32_t iv_prefix = provider.ConsumeIntegral<uint32_t>();
     uint64_t total_bytes = provider.ConsumeIntegralInRange<uint64_t>(0, 1000000);
diff --git a/src/test/fuzz/crypto_poly1305.cpp b/src/test/fuzz/crypto_poly1305.cpp
index f49729a34b..6ce6648f56 100644
--- a/src/test/fuzz/crypto_poly1305.cpp
+++ b/src/test/fuzz/crypto_poly1305.cpp
@@ -14,14 +14,13 @@ FUZZ_TARGET(crypto_poly1305)
 {
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
 
-    const std::vector<uint8_t> key = ConsumeFixedLengthByteVector(fuzzed_data_provider, Poly1305::KEYLEN);
-    const std::vector<uint8_t> in = ConsumeRandomLengthByteVector(fuzzed_data_provider);
+    const auto key = ConsumeFixedLengthByteVector<std::byte>(fuzzed_data_provider, Poly1305::KEYLEN);
+    const auto in = ConsumeRandomLengthByteVector<std::byte>(fuzzed_data_provider);
 
     std::vector<std::byte> tag_out(Poly1305::TAGLEN);
-    Poly1305{MakeByteSpan(key)}.Update(MakeByteSpan(in)).Finalize(tag_out);
+    Poly1305{key}.Update(in).Finalize(tag_out);
 }
 
-
 FUZZ_TARGET(crypto_poly1305_split)
 {
     FuzzedDataProvider provider{buffer.data(), buffer.size()};
@@ -36,10 +35,10 @@ FUZZ_TARGET(crypto_poly1305_split)
 
     // Process input in pieces.
     LIMITED_WHILE(provider.remaining_bytes(), 100) {
-        auto in = provider.ConsumeRandomLengthString();
-        poly_split.Update(MakeByteSpan(in));
+        auto in = ConsumeRandomLengthByteVector<std::byte>(provider);
+        poly_split.Update(in);
         // Update total_input to match what was processed.
-        total_input.insert(total_input.end(), MakeByteSpan(in).begin(), MakeByteSpan(in).end());
+        total_input.insert(total_input.end(), in.begin(), in.end());
     }
 
     // Process entire input at once.
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index 736311ed55..5d27d2a180 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -53,12 +53,16 @@ auto& PickValue(FuzzedDataProvider& fuzzed_data_provider, Collection& col)
     return *it;
 }
 
-[[nodiscard]] inline std::vector<uint8_t> ConsumeRandomLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const std::optional<size_t>& max_length = std::nullopt) noexcept
+template<typename B = uint8_t>
+[[nodiscard]] inline std::vector<B> ConsumeRandomLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const std::optional<size_t>& max_length = std::nullopt) noexcept
 {
+    static_assert(sizeof(B) == 1);
     const std::string s = max_length ?
                               fuzzed_data_provider.ConsumeRandomLengthString(*max_length) :
                               fuzzed_data_provider.ConsumeRandomLengthString();
-    return {s.begin(), s.end()};
+    std::vector<B> ret(s.size());
+    std::copy(s.begin(), s.end(), reinterpret_cast<char*>(ret.data()));
+    return ret;
 }
 
 [[nodiscard]] inline std::vector<bool> ConsumeRandomLengthBitVector(FuzzedDataProvider& fuzzed_data_provider, const std::optional<size_t>& max_length = std::nullopt) noexcept
@@ -209,14 +213,13 @@ inline void SetFuzzedErrNo(FuzzedDataProvider& fuzzed_data_provider) noexcept
  * Returns a byte vector of specified size regardless of the number of remaining bytes available
  * from the fuzzer. Pads with zero value bytes if needed to achieve the specified size.
  */
-[[nodiscard]] inline std::vector<uint8_t> ConsumeFixedLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const size_t length) noexcept
+template<typename B = uint8_t>
+[[nodiscard]] inline std::vector<B> ConsumeFixedLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const size_t length) noexcept
 {
-    std::vector<uint8_t> result(length);
-    const std::vector<uint8_t> random_bytes = fuzzed_data_provider.ConsumeBytes<uint8_t>(length);
-    if (!random_bytes.empty()) {
-        std::memcpy(result.data(), random_bytes.data(), random_bytes.size());
-    }
-    return result;
+    static_assert(sizeof(B) == 1);
+    auto random_bytes = fuzzed_data_provider.ConsumeBytes<B>(length);
+    random_bytes.resize(length);
+    return random_bytes;
 }
 
 class FuzzedFileProvider