diff --git a/src/security/certificate-extension.hpp b/src/security/certificate-extension.hpp
index cad811f..4a42eac 100644
--- a/src/security/certificate-extension.hpp
+++ b/src/security/certificate-extension.hpp
@@ -52,6 +52,7 @@
     }
   };
 
+  explicit
   CertificateExtension(CryptoPP::BufferedTransformation& in)
   {
     decode(in);