diff --git a/api/include/opentelemetry/trace/propagation/detail/hex.h b/api/include/opentelemetry/trace/propagation/detail/hex.h
index c8bd58f..aecdedd 100644
--- a/api/include/opentelemetry/trace/propagation/detail/hex.h
+++ b/api/include/opentelemetry/trace/propagation/detail/hex.h
@@ -5,6 +5,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <cstdint>
 
 #include "opentelemetry/nostd/string_view.h"
 #include "opentelemetry/version.h"