diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2ca9182..ae3d263 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@ project(nac-abe
         DESCRIPTION "NDN Name-based access control - attribute based encryption library")
 
 # flags
-set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED True)
 if (HAVE_TESTS)
     add_compile_definitions(HAVE_TESTS)
diff --git a/src/trust-config.cpp b/src/trust-config.cpp
index 98e826a..3d68398 100644
--- a/src/trust-config.cpp
+++ b/src/trust-config.cpp
@@ -68,7 +68,7 @@ TrustConfig::addOrUpdateCertificate(const security::Certificate& certificate)
   }
 }
 
-optional<security::Certificate>
+std::optional<security::Certificate>
 TrustConfig::findCertificate(const Name& identityName) const
 {
   auto search = m_knownIdentities.find(identityName);
@@ -76,7 +76,7 @@ TrustConfig::findCertificate(const Name& identityName) const
     return make_optional(search->second);
   }
   else {
-    return nullopt;
+    return std::nullopt;
   }
 }
 
diff --git a/src/trust-config.hpp b/src/trust-config.hpp
index e71830d..61fc9f5 100644
--- a/src/trust-config.hpp
+++ b/src/trust-config.hpp
@@ -37,7 +37,7 @@ class TrustConfig
   void
   addOrUpdateCertificate(const security::Certificate& certificate);
 
-  optional<security::Certificate>
+  std::optional<security::Certificate>
   findCertificate(const Name& identityName) const;
 
 private: