diff --git a/src/message/native_types.cpp b/src/message/native_types.cpp
index 08ccd02..bdb9354 100644
--- a/src/message/native_types.cpp
+++ b/src/message/native_types.cpp
@@ -88,7 +88,7 @@
         {
             return "";
         }
-        out.append(1, (ch << 4) | cl);
+        out.append(1, static_cast<char>((ch << 4) | cl));
         i += 2;
     }
     return out;