diff --git a/barretenberg/cpp/src/barretenberg/vm/avm_trace/AvmMini_opcode.cpp b/barretenberg/cpp/src/barretenberg/vm/avm_trace/AvmMini_opcode.cpp
index 6c530a765b1..5ebc445ee9b 100644
--- a/barretenberg/cpp/src/barretenberg/vm/avm_trace/AvmMini_opcode.cpp
+++ b/barretenberg/cpp/src/barretenberg/vm/avm_trace/AvmMini_opcode.cpp
@@ -1,7 +1,8 @@
 #include "AvmMini_opcode.hpp"
 
 #include <cstdint>
-#include <format>
+#include <iomanip>
+#include <sstream>
 
 namespace avm_trace {
 
@@ -154,7 +155,10 @@ bool Bytecode::has_in_tag(OpCode const op_code)
 
 std::string to_hex(OpCode opcode)
 {
-    return std::format("{:02x}", static_cast<uint8_t>(opcode));
+    std::ostringstream stream;
+    // pad with 0s to fill exactly 2 hex characters
+    stream << std::setfill('0') << std::setw(2) << std::hex << (static_cast<uint8_t>(opcode) & 0xFF);
+    return stream.str();
 }
 
 } // namespace avm_trace
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