diff --git a/src/security/conf/checker.hpp b/src/security/conf/checker.hpp
index 12017e2..a9ab2a9 100644
--- a/src/security/conf/checker.hpp
+++ b/src/security/conf/checker.hpp
@@ -193,6 +193,7 @@
 class HierarchicalChecker : public CustomizedChecker
 {
 public:
+  explicit
   HierarchicalChecker(uint32_t sigType)
     : CustomizedChecker(sigType,
         make_shared<HyperKeyLocatorNameChecker>("^(<>*)$", "\\1",
diff --git a/src/security/conf/key-locator-checker.hpp b/src/security/conf/key-locator-checker.hpp
index 52cf888..ff9e5fc 100644
--- a/src/security/conf/key-locator-checker.hpp
+++ b/src/security/conf/key-locator-checker.hpp
@@ -148,6 +148,7 @@
 class RegexKeyLocatorNameChecker : public KeyLocatorChecker
 {
 public:
+  explicit
   RegexKeyLocatorNameChecker(const Regex& regex)
     : m_regex(regex)
   {
diff --git a/src/security/conf/rule.hpp b/src/security/conf/rule.hpp
index 6ed5808..31d81f7 100644
--- a/src/security/conf/rule.hpp
+++ b/src/security/conf/rule.hpp
@@ -36,6 +36,7 @@
 class Rule
 {
 public:
+  explicit
   Rule(const std::string& id)
     : m_id(id)
   {