diff --git a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfiguration.java b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfiguration.java
index ce89524c27..70bc8c50c6 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfiguration.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfiguration.java
@@ -45,7 +45,6 @@ public class RestTemplateAutoConfiguration {
 
 	@Bean
 	@Lazy
-	@ConditionalOnMissingBean
 	public RestTemplateBuilderConfigurer restTemplateBuilderConfigurer(
 			ObjectProvider<HttpMessageConverters> messageConverters,
 			ObjectProvider<RestTemplateCustomizer> restTemplateCustomizers,
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfigurationTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfigurationTests.java
index a80f93a737..8e576929f2 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfigurationTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/client/RestTemplateAutoConfigurationTests.java
@@ -21,6 +21,7 @@ import java.util.List;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.beans.factory.support.BeanDefinitionOverrideException;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
 import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
@@ -65,6 +66,14 @@ class RestTemplateAutoConfigurationTests {
 			.isTrue());
 	}
 
+	@Test
+	void shouldFailOnCustomRestTemplateBuilderConfigurer() {
+		this.contextRunner.withUserConfiguration(RestTemplateCustomConfigurerConfig.class)
+			.run((context) -> assertThat(context).getFailure()
+				.isInstanceOf(BeanDefinitionOverrideException.class)
+				.hasMessageContaining("with name 'restTemplateBuilderConfigurer'"));
+	}
+
 	@Test
 	void restTemplateBuilderShouldBeLazilyDefined() {
 		this.contextRunner
@@ -263,6 +272,16 @@ class RestTemplateAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class RestTemplateCustomConfigurerConfig {
+
+		@Bean
+		RestTemplateBuilderConfigurer restTemplateBuilderConfigurer() {
+			return new RestTemplateBuilderConfigurer();
+		}
+
+	}
+
 	static class CustomHttpMessageConverter extends StringHttpMessageConverter {
 
 	}