Implement encoding/decoding SignedInfo content Type.
diff --git a/ndn-cpp/c/errors.c b/ndn-cpp/c/errors.c
index 6811b6a..af70f56 100644
--- a/ndn-cpp/c/errors.c
+++ b/ndn-cpp/c/errors.c
@@ -48,6 +48,8 @@
     return      "DynamicUCharArray realloc failed";
   case NDN_ERROR_unrecognized_ndn_ExcludeType:
     return      "unrecognized ndn_ExcludeType";
+  case NDN_ERROR_unrecognized_ndn_ContentType:
+    return      "unrecognized ndn_ContentType";
   case NDN_ERROR_unrecognized_ndn_KeyLocatorType:
     return      "unrecognized ndn_KeyLocatorType";
   case NDN_ERROR_unrecognized_ndn_KeyNameType: