diff --git a/lib/EAPBase/include/Config.h b/lib/EAPBase/include/Config.h
index b66701c..c8f3d64 100644
--- a/lib/EAPBase/include/Config.h
+++ b/lib/EAPBase/include/Config.h
@@ -311,7 +311,7 @@ namespace eap
         ///
         /// \returns One of `eap::type_t` constants.
         ///
-        virtual type_t get_method_id() = 0;
+        virtual type_t get_method_id() const = 0;
 
     public:
         bool m_allow_save;                      ///< Are credentials allowed to be saved to Windows Credential Manager?
diff --git a/lib/PAP/include/Config.h b/lib/PAP/include/Config.h
index 2869b4b..14ed3f4 100644
--- a/lib/PAP/include/Config.h
+++ b/lib/PAP/include/Config.h
@@ -114,14 +114,14 @@ namespace eap
         ///
         /// \returns Pointer to cloned configuration
         ///
-        virtual config* clone() const { return new config_pap(*this); }
+        virtual config* clone() const;
 
         ///
         /// Returns EAP method type of this configuration
         ///
         /// \returns `eap::type_pap`
         ///
-        virtual eap::type_t get_method_id() { return eap::type_pap; }
+        virtual eap::type_t get_method_id() const;
     };
 }
 
diff --git a/lib/PAP/include/Credentials.h b/lib/PAP/include/Credentials.h
index 40402e8..3c41a46 100644
--- a/lib/PAP/include/Credentials.h
+++ b/lib/PAP/include/Credentials.h
@@ -87,7 +87,7 @@ namespace eap
         ///
         /// \returns Pointer to cloned credentials
         ///
-        virtual config* clone() const { return new credentials_pap(*this); }
+        virtual config* clone() const;
 
         /// \name Storage
         /// @{
@@ -95,7 +95,7 @@ namespace eap
         ///
         /// Return target suffix for Windows Credential Manager credential name
         ///
-        virtual LPCTSTR target_suffix() const { return _T("PAP"); }
+        virtual LPCTSTR target_suffix() const;
 
         /// @}
     };
diff --git a/lib/PAP/src/Config.cpp b/lib/PAP/src/Config.cpp
index 4f6175a..c8eac67 100644
--- a/lib/PAP/src/Config.cpp
+++ b/lib/PAP/src/Config.cpp
@@ -60,3 +60,13 @@ eap::config_pap& eap::config_pap::operator=(_Inout_ config_pap &&other)
 }
 
 
+eap::config* eap::config_pap::clone() const
+{
+    return new config_pap(*this);
+}
+
+
+eap::type_t eap::config_pap::get_method_id() const
+{
+    return eap::type_pap;
+}
diff --git a/lib/PAP/src/Credentials.cpp b/lib/PAP/src/Credentials.cpp
index ef1337b..1e619c9 100644
--- a/lib/PAP/src/Credentials.cpp
+++ b/lib/PAP/src/Credentials.cpp
@@ -58,3 +58,15 @@ eap::credentials_pap& eap::credentials_pap::operator=(_Inout_ credentials_pap &&
 
     return *this;
 }
+
+
+eap::config* eap::credentials_pap::clone() const
+{
+    return new credentials_pap(*this);
+}
+
+
+LPCTSTR eap::credentials_pap::target_suffix() const
+{
+    return _T("PAP");
+}
diff --git a/lib/TLS/include/Config.h b/lib/TLS/include/Config.h
index 3519224..a52678a 100644
--- a/lib/TLS/include/Config.h
+++ b/lib/TLS/include/Config.h
@@ -117,7 +117,7 @@ namespace eap
         ///
         /// \returns Pointer to cloned configuration
         ///
-        virtual config* clone() const { return new config_tls(*this); }
+        virtual config* clone() const;
 
         /// \name XML configuration management
         /// @{
@@ -154,7 +154,7 @@ namespace eap
         ///
         /// \returns `eap::type_tls`
         ///
-        virtual eap::type_t get_method_id() { return eap::type_tls; }
+        virtual eap::type_t get_method_id() const;
 
         ///
         /// Adds CA to the list of trusted root CA's
diff --git a/lib/TLS/include/Credentials.h b/lib/TLS/include/Credentials.h
index 9797fce..d5f3625 100644
--- a/lib/TLS/include/Credentials.h
+++ b/lib/TLS/include/Credentials.h
@@ -113,7 +113,7 @@ namespace eap
         ///
         /// \returns Pointer to cloned credentials
         ///
-        virtual config* clone() const { return new credentials_tls(*this); }
+        virtual config* clone() const;
 
         ///
         /// Resets credentials
diff --git a/lib/TLS/src/Config.cpp b/lib/TLS/src/Config.cpp
index cae31d0..6591a6f 100644
--- a/lib/TLS/src/Config.cpp
+++ b/lib/TLS/src/Config.cpp
@@ -73,6 +73,12 @@ eap::config_tls& eap::config_tls::operator=(_Inout_ eap::config_tls &&other)
 }
 
 
+eap::config* eap::config_tls::clone() const
+{
+    return new config_tls(*this);
+}
+
+
 DWORD eap::config_tls::save(_In_ IXMLDOMDocument *pDoc, _In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppEapError) const
 {
     const bstr bstrNamespace(L"urn:ietf:params:xml:ns:yang:ietf-eap-metadata");
@@ -178,6 +184,12 @@ DWORD eap::config_tls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppE
 }
 
 
+eap::type_t eap::config_tls::get_method_id() const
+{
+    return eap::type_tls;
+}
+
+
 bool eap::config_tls::add_trusted_ca(_In_  DWORD dwCertEncodingType, _In_  const BYTE *pbCertEncoded, _In_  DWORD cbCertEncoded)
 {
     cert_context cert;
diff --git a/lib/TLS/src/Credentials.cpp b/lib/TLS/src/Credentials.cpp
index a0b64d9..f3ebac6 100644
--- a/lib/TLS/src/Credentials.cpp
+++ b/lib/TLS/src/Credentials.cpp
@@ -69,6 +69,11 @@ eap::credentials_tls& eap::credentials_tls::operator=(_Inout_ credentials_tls &&
 }
 
 
+eap::config* eap::credentials_tls::clone() const
+{
+    return new credentials_tls(*this);
+}
+
 
 void eap::credentials_tls::clear()
 {
@@ -83,7 +88,6 @@ bool eap::credentials_tls::empty() const
 }
 
 
-
 DWORD eap::credentials_tls::save(_In_ IXMLDOMDocument *pDoc, _In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppEapError) const
 {
     const bstr bstrNamespace(L"urn:ietf:params:xml:ns:yang:ietf-eap-metadata");
@@ -100,7 +104,6 @@ DWORD eap::credentials_tls::save(_In_ IXMLDOMDocument *pDoc, _In_ IXMLDOMNode *p
 }
 
 
-
 DWORD eap::credentials_tls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppEapError)
 {
     assert(pConfigRoot);
diff --git a/lib/TTLS/include/Config.h b/lib/TTLS/include/Config.h
index 5b1dd80..9709d8a 100644
--- a/lib/TTLS/include/Config.h
+++ b/lib/TTLS/include/Config.h
@@ -118,7 +118,7 @@ namespace eap {
         ///
         /// \returns Pointer to cloned configuration
         ///
-        virtual config* clone() const { return new config_ttls(*this); }
+        virtual config* clone() const;
 
         /// \name XML configuration management
         /// @{
@@ -155,7 +155,7 @@ namespace eap {
         ///
         /// \returns `eap::type_ttls`
         ///
-        virtual eap::type_t get_method_id() { return eap::type_ttls; }
+        virtual eap::type_t get_method_id() const;
 
     public:
         config_method *m_inner;    ///< Inner authentication configuration
diff --git a/lib/TTLS/include/Credentials.h b/lib/TTLS/include/Credentials.h
index 876fd56..cfe5efb 100644
--- a/lib/TTLS/include/Credentials.h
+++ b/lib/TTLS/include/Credentials.h
@@ -80,7 +80,7 @@ namespace eap
         ///
         /// \returns Pointer to cloned credentials
         ///
-        virtual config* clone() const { return new credentials_ttls(*this); }
+        virtual config* clone() const;
 
         ///
         /// Resets credentials
diff --git a/lib/TTLS/src/Config.cpp b/lib/TTLS/src/Config.cpp
index bd32445..31d39ce 100644
--- a/lib/TTLS/src/Config.cpp
+++ b/lib/TTLS/src/Config.cpp
@@ -82,6 +82,12 @@ eap::config_ttls& eap::config_ttls::operator=(_Inout_ config_ttls &&other)
 }
 
 
+eap::config* eap::config_ttls::clone() const
+{
+    return new config_ttls(*this);
+}
+
+
 DWORD eap::config_ttls::save(_In_ IXMLDOMDocument *pDoc, _In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppEapError) const
 {
     const bstr bstrNamespace(L"urn:ietf:params:xml:ns:yang:ietf-eap-metadata");
@@ -147,3 +153,9 @@ DWORD eap::config_ttls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **pp
 
     return config_tls::load(pConfigRoot, ppEapError);
 }
+
+
+eap::type_t eap::config_ttls::get_method_id() const
+{
+    return eap::type_ttls;
+}
diff --git a/lib/TTLS/src/Credentials.cpp b/lib/TTLS/src/Credentials.cpp
index 8ef08a7..b771231 100644
--- a/lib/TTLS/src/Credentials.cpp
+++ b/lib/TTLS/src/Credentials.cpp
@@ -75,6 +75,11 @@ eap::credentials_ttls& eap::credentials_ttls::operator=(_Inout_ credentials_ttls
 }
 
 
+eap::config* eap::credentials_ttls::clone() const
+{
+    return new credentials_ttls(*this);
+}
+
 
 void eap::credentials_ttls::clear()
 {
@@ -90,7 +95,6 @@ bool eap::credentials_ttls::empty() const
 }
 
 
-
 DWORD eap::credentials_ttls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppEapError)
 {
     assert(pConfigRoot);