diff --git a/sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java b/sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java
index d64673b240..7f2385b67e 100755
--- a/sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java
+++ b/sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java
@@ -1947,7 +1947,7 @@ private CharSequence generateMessageFlyweightCode(final String className, final
             "        return %2$s;\n" +
             "    }\n\n" +
 
-            "    SBE_NODISCARD static SBE_CONSTEXPR %1$s sbeBlockAndHeaderLength() SBE_NOEXCEPT\n" +
+            "    SBE_NODISCARD static SBE_CONSTEXPR std::uint64_t sbeBlockAndHeaderLength() SBE_NOEXCEPT\n" +
             "    {\n" +
             "        return messageHeader::encodedLength() + sbeBlockLength();\n" +
             "    }\n\n" +