diff --git a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/OAuth2ClientJackson2Module.java b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/OAuth2ClientJackson2Module.java
index 4c8158247a..ba1eaacd2c 100644
--- a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/OAuth2ClientJackson2Module.java
+++ b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/OAuth2ClientJackson2Module.java
@@ -16,8 +16,6 @@
 
 package org.springframework.security.oauth2.client.jackson2;
 
-import java.util.Collections;
-
 import com.fasterxml.jackson.core.Version;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 
@@ -97,8 +95,6 @@ public class OAuth2ClientJackson2Module extends SimpleModule {
 	@Override
 	public void setupModule(SetupContext context) {
 		SecurityJackson2Modules.enableDefaultTyping(context.getOwner());
-		context.setMixInAnnotations(Collections.unmodifiableMap(Collections.emptyMap()).getClass(),
-				UnmodifiableMapMixin.class);
 		context.setMixInAnnotations(OAuth2AuthorizationRequest.class, OAuth2AuthorizationRequestMixin.class);
 		context.setMixInAnnotations(ClientRegistration.class, ClientRegistrationMixin.class);
 		context.setMixInAnnotations(OAuth2AccessToken.class, OAuth2AccessTokenMixin.class);
diff --git a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/UnmodifiableMapDeserializer.java b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/UnmodifiableMapDeserializer.java
deleted file mode 100644
index d44b9c7278..0000000000
--- a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/UnmodifiableMapDeserializer.java
+++ /dev/null
@@ -1,54 +0,0 @@
-/*
- * Copyright 2002-2020 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.springframework.security.oauth2.client.jackson2;
-
-import java.io.IOException;
-import java.util.Collections;
-import java.util.LinkedHashMap;
-import java.util.Map;
-
-import com.fasterxml.jackson.core.JsonParser;
-import com.fasterxml.jackson.databind.DeserializationContext;
-import com.fasterxml.jackson.databind.JsonDeserializer;
-import com.fasterxml.jackson.databind.JsonNode;
-import com.fasterxml.jackson.databind.ObjectMapper;
-
-/**
- * A {@code JsonDeserializer} for {@link Collections#unmodifiableMap(Map)}.
- *
- * @author Joe Grandja
- * @since 5.3
- * @see Collections#unmodifiableMap(Map)
- * @see UnmodifiableMapMixin
- */
-final class UnmodifiableMapDeserializer extends JsonDeserializer<Map<?, ?>> {
-
-	@Override
-	public Map<?, ?> deserialize(JsonParser parser, DeserializationContext context) throws IOException {
-		ObjectMapper mapper = (ObjectMapper) parser.getCodec();
-		JsonNode mapNode = mapper.readTree(parser);
-		Map<String, Object> result = new LinkedHashMap<>();
-		if (mapNode != null && mapNode.isObject()) {
-			Iterable<Map.Entry<String, JsonNode>> fields = mapNode::fields;
-			for (Map.Entry<String, JsonNode> field : fields) {
-				result.put(field.getKey(), mapper.readValue(field.getValue().traverse(mapper), Object.class));
-			}
-		}
-		return Collections.unmodifiableMap(result);
-	}
-
-}
diff --git a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/UnmodifiableMapMixin.java b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/UnmodifiableMapMixin.java
deleted file mode 100644
index 95941cc7e0..0000000000
--- a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/jackson2/UnmodifiableMapMixin.java
+++ /dev/null
@@ -1,45 +0,0 @@
-/*
- * Copyright 2002-2020 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.springframework.security.oauth2.client.jackson2;
-
-import java.util.Collections;
-import java.util.Map;
-
-import com.fasterxml.jackson.annotation.JsonCreator;
-import com.fasterxml.jackson.annotation.JsonTypeInfo;
-import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
-
-/**
- * This mixin class is used to serialize/deserialize
- * {@link Collections#unmodifiableMap(Map)}. It also registers a custom deserializer
- * {@link UnmodifiableMapDeserializer}.
- *
- * @author Joe Grandja
- * @since 5.3
- * @see Collections#unmodifiableMap(Map)
- * @see UnmodifiableMapDeserializer
- * @see OAuth2ClientJackson2Module
- */
-@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS)
-@JsonDeserialize(using = UnmodifiableMapDeserializer.class)
-abstract class UnmodifiableMapMixin {
-
-	@JsonCreator
-	UnmodifiableMapMixin(Map<?, ?> map) {
-	}
-
-}