diff --git a/src/test/fuzz/base_encode_decode.cpp b/src/test/fuzz/base_encode_decode.cpp
index 06b249fb8d3..69caac58100 100644
--- a/src/test/fuzz/base_encode_decode.cpp
+++ b/src/test/fuzz/base_encode_decode.cpp
@@ -6,6 +6,7 @@
 
 #include <base58.h>
 #include <psbt.h>
+#include <span.h>
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <util/strencodings.h>
 #include <util/string.h>
@@ -19,42 +20,40 @@ using util::TrimStringView;
 
 FUZZ_TARGET(base58_encode_decode)
 {
-    FuzzedDataProvider provider(buffer.data(), buffer.size());
-    const std::string random_string{provider.ConsumeRandomLengthString(1000)};
-    const int max_ret_len{provider.ConsumeIntegralInRange<int>(-1, 1000)};
+    FuzzedDataProvider provider{buffer.data(), buffer.size()};
+    const auto random_string{provider.ConsumeRandomLengthString(100)};
+    const int max_ret_len{provider.ConsumeIntegralInRange<int>(-1, 100)};
 
     // Decode/Encode roundtrip
-    std::vector<unsigned char> decoded;
-    if (DecodeBase58(random_string, decoded, max_ret_len)) {
+    if (std::vector<unsigned char> decoded; DecodeBase58(random_string, decoded, max_ret_len)) {
         const auto encoded_string{EncodeBase58(decoded)};
         assert(encoded_string == TrimStringView(random_string));
-        assert(encoded_string.empty() || !DecodeBase58(encoded_string, decoded, provider.ConsumeIntegralInRange<int>(0, decoded.size() - 1)));
+        assert(decoded.empty() || !DecodeBase58(encoded_string, decoded, provider.ConsumeIntegralInRange<int>(0, decoded.size() - 1)));
     }
     // Encode/Decode roundtrip
-    const auto encoded{EncodeBase58(buffer)};
+    const auto encoded{EncodeBase58(MakeUCharSpan(random_string))};
     std::vector<unsigned char> roundtrip_decoded;
-    assert(DecodeBase58(encoded, roundtrip_decoded, buffer.size())
-        && std::ranges::equal(roundtrip_decoded, buffer));
+    assert(DecodeBase58(encoded, roundtrip_decoded, random_string.size())
+        && std::ranges::equal(roundtrip_decoded, MakeUCharSpan(random_string)));
 }
 
 FUZZ_TARGET(base58check_encode_decode)
 {
-    FuzzedDataProvider provider(buffer.data(), buffer.size());
-    const std::string random_string{provider.ConsumeRandomLengthString(1000)};
-    const int max_ret_len{provider.ConsumeIntegralInRange<int>(-1, 1000)};
+    FuzzedDataProvider provider{buffer.data(), buffer.size()};
+    const auto random_string{provider.ConsumeRandomLengthString(100)};
+    const int max_ret_len{provider.ConsumeIntegralInRange<int>(-1, 100)};
 
     // Decode/Encode roundtrip
-    std::vector<unsigned char> decoded;
-    if (DecodeBase58Check(random_string, decoded, max_ret_len)) {
+    if (std::vector<unsigned char> decoded; DecodeBase58Check(random_string, decoded, max_ret_len)) {
         const auto encoded_string{EncodeBase58Check(decoded)};
         assert(encoded_string == TrimStringView(random_string));
-        assert(encoded_string.empty() || !DecodeBase58Check(encoded_string, decoded, provider.ConsumeIntegralInRange<int>(0, decoded.size() - 1)));
+        assert(decoded.empty() || !DecodeBase58Check(encoded_string, decoded, provider.ConsumeIntegralInRange<int>(0, decoded.size() - 1)));
     }
     // Encode/Decode roundtrip
-    const auto encoded{EncodeBase58Check(buffer)};
+    const auto encoded{EncodeBase58Check(MakeUCharSpan(random_string))};
     std::vector<unsigned char> roundtrip_decoded;
-    assert(DecodeBase58Check(encoded, roundtrip_decoded, buffer.size())
-        && std::ranges::equal(roundtrip_decoded, buffer));
+    assert(DecodeBase58Check(encoded, roundtrip_decoded, random_string.size())
+        && std::ranges::equal(roundtrip_decoded, MakeUCharSpan(random_string)));
 }
 
 FUZZ_TARGET(base32_encode_decode)