diff --git a/source/birchwood/protocol/messages.d b/source/birchwood/protocol/messages.d
index 603708e..e91226e 100644
--- a/source/birchwood/protocol/messages.d
+++ b/source/birchwood/protocol/messages.d
@@ -608,4 +608,17 @@ public final class Message
     {
         return replyType;
     }
+}
+
+version(unittest)
+{
+    // Contains illegal characters
+    string badString1 = "doos"~"bruh"~"lek"~cast(string)[10]~"ker";
+    string badString2 = "doos"~"bruh"~"lek"~cast(string)[13]~"ker";
+}
+
+unittest
+{
+    assert(Message.hasIllegalCharacters(badString1) == true);
+    assert(Message.hasIllegalCharacters(badString2) == true);
 }
\ No newline at end of file