diff --git a/src/protocol-detail/error.hpp b/src/protocol-detail/error.hpp
index 8a2cda0..d39fe1a 100644
--- a/src/protocol-detail/error.hpp
+++ b/src/protocol-detail/error.hpp
@@ -39,6 +39,9 @@
    */
   static std::tuple<ErrorCode, std::string>
   decodefromDataContent(const Block& block);
+
+  static bool
+  isErrorContent(const Block& block);
 };
 
 }  // namespace ndncert