diff --git a/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java b/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java
index 4a6243d16e..0d3f9941f3 100644
--- a/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java
+++ b/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java
@@ -118,6 +118,8 @@
 import org.springframework.security.oauth2.server.resource.introspection.OAuth2IntrospectionAuthenticatedPrincipal;
 import org.springframework.security.saml2.Saml2Exception;
 import org.springframework.security.saml2.core.Saml2Error;
+import org.springframework.security.saml2.core.Saml2X509Credential;
+import org.springframework.security.saml2.credentials.TestSaml2X509Credentials;
 import org.springframework.security.saml2.provider.service.authentication.DefaultSaml2AuthenticatedPrincipal;
 import org.springframework.security.saml2.provider.service.authentication.Saml2Authentication;
 import org.springframework.security.saml2.provider.service.authentication.Saml2AuthenticationException;
@@ -127,6 +129,7 @@
 import org.springframework.security.saml2.provider.service.authentication.TestSaml2PostAuthenticationRequests;
 import org.springframework.security.saml2.provider.service.authentication.TestSaml2RedirectAuthenticationRequests;
 import org.springframework.security.saml2.provider.service.registration.RelyingPartyRegistration;
+import org.springframework.security.saml2.provider.service.registration.RelyingPartyRegistration.AssertingPartyDetails;
 import org.springframework.security.saml2.provider.service.registration.TestRelyingPartyRegistrations;
 import org.springframework.security.web.authentication.WebAuthenticationDetails;
 import org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationToken;
@@ -324,6 +327,10 @@ class SpringSecurityCoreVersionSerializableTests {
 				(r) -> TestSaml2PostAuthenticationRequests.create());
 		generatorByClassName.put(Saml2RedirectAuthenticationRequest.class,
 				(r) -> TestSaml2RedirectAuthenticationRequests.create());
+		generatorByClassName.put(Saml2X509Credential.class,
+				(r) -> TestSaml2X509Credentials.relyingPartyVerifyingCredential());
+		generatorByClassName.put(AssertingPartyDetails.class,
+				(r) -> TestRelyingPartyRegistrations.full().build().getAssertingPartyMetadata());
 		generatorByClassName.put(RelyingPartyRegistration.class, (r) -> TestRelyingPartyRegistrations.full().build());
 
 		// web
diff --git a/config/src/test/resources/serialized/6.5.x/org.springframework.security.saml2.core.Saml2X509Credential.serialized b/config/src/test/resources/serialized/6.5.x/org.springframework.security.saml2.core.Saml2X509Credential.serialized
new file mode 100644
index 0000000000..736cb69fc1
Binary files /dev/null and b/config/src/test/resources/serialized/6.5.x/org.springframework.security.saml2.core.Saml2X509Credential.serialized differ
diff --git a/config/src/test/resources/serialized/6.5.x/org.springframework.security.saml2.provider.service.registration.RelyingPartyRegistration$AssertingPartyDetails.serialized b/config/src/test/resources/serialized/6.5.x/org.springframework.security.saml2.provider.service.registration.RelyingPartyRegistration$AssertingPartyDetails.serialized
new file mode 100644
index 0000000000..55aff67094
Binary files /dev/null and b/config/src/test/resources/serialized/6.5.x/org.springframework.security.saml2.provider.service.registration.RelyingPartyRegistration$AssertingPartyDetails.serialized differ