If KeyLocator is a KeyName, allow the key name data to be omitted.
diff --git a/ndn-cpp/c/key.h b/ndn-cpp/c/key.h
index 5bfe05e..f6df357 100644
--- a/ndn-cpp/c/key.h
+++ b/ndn-cpp/c/key.h
@@ -40,7 +40,7 @@
     */
   unsigned int keyDataLength;  /**< The length of keyData. */
   struct ndn_Name keyName;     /**< The key name (only used if type is ndn_KeyLocatorType_KEYNAME.) */
-  ndn_KeyNameType keyNameType; /**< The type of data for keyName (only used if type is ndn_KeyLocatorType_KEYNAME.) */
+  ndn_KeyNameType keyNameType; /**< The type of data for keyName, -1 for none. (only used if type is ndn_KeyLocatorType_KEYNAME.) */
 };
 
 /**