diff --git a/src/security/sec-tpm-file.hpp b/src/security/sec-tpm-file.hpp
index 38ca1b5..d878ad6 100644
--- a/src/security/sec-tpm-file.hpp
+++ b/src/security/sec-tpm-file.hpp
@@ -45,6 +45,7 @@
     }
   };
 
+  explicit
   SecTpmFile(const std::string& dir = "");
 
   virtual