diff --git a/src/impl/btc/coin/node.hpp b/src/impl/btc/coin/node.hpp
index e7b78abdd..940795d1b 100644
--- a/src/impl/btc/coin/node.hpp
+++ b/src/impl/btc/coin/node.hpp
@@ -128,7 +128,11 @@ class Node : public btc::interfaces::Node
     {
         if (!m_rpc)
             return false;
-        return m_rpc->submit_block_hex(HexStr(block_bytes), /*ignore_failure=*/true);
+        // MSVC: disambiguate HexStr overload (std::vector<unsigned char> is viable
+        // for all span overloads). Feed the exact byte span the uint8_t overload wants.
+        return m_rpc->submit_block_hex(
+            HexStr(Span<const uint8_t>(block_bytes.data(), block_bytes.size())),
+            /*ignore_failure=*/true);
     }
 
     /// Broadcast a WON block with FALLBACK semantics: P2P relay is primary,