diff --git a/src/hash.h b/src/hash.h
--- a/src/hash.h
+++ b/src/hash.h
@@ -200,8 +200,7 @@
     return ss.GetHash();
 }
 
-uint32_t MurmurHash3(uint32_t nHashSeed,
-                     const std::vector<uint8_t> &vDataToHash);
+uint32_t MurmurHash3(uint32_t nHashSeed, Span<const uint8_t> vDataToHash);
 
 void BIP32Hash(const ChainCode &chainCode, uint32_t nChild, uint8_t header,
                const uint8_t data[32], uint8_t output[64]);
diff --git a/src/hash.cpp b/src/hash.cpp
--- a/src/hash.cpp
+++ b/src/hash.cpp
@@ -10,8 +10,7 @@
     return (x << r) | (x >> (32 - r));
 }
 
-uint32_t MurmurHash3(uint32_t nHashSeed,
-                     const std::vector<uint8_t> &vDataToHash) {
+uint32_t MurmurHash3(uint32_t nHashSeed, Span<const uint8_t> vDataToHash) {
     // The following is MurmurHash3 (x86_32), see
     // http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
     uint32_t h1 = nHashSeed;