diff --git a/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultWebTestClientBuilder.java b/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultWebTestClientBuilder.java
index 5d62cd4b073..719012d8f4d 100644
--- a/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultWebTestClientBuilder.java
+++ b/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultWebTestClientBuilder.java
@@ -215,7 +215,7 @@ class DefaultWebTestClientBuilder implements WebTestClient.Builder {
 	}
 
 	@Override
-	public WebTestClient.Builder apiVersionInserter(ApiVersionInserter apiVersionInserter) {
+	public WebTestClient.Builder apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter) {
 		this.apiVersionInserter = apiVersionInserter;
 		return this;
 	}
diff --git a/spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java b/spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java
index d28c8e79bb1..49ca1f1bc57 100644
--- a/spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java
+++ b/spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java
@@ -453,7 +453,7 @@ public interface WebTestClient {
 		 * @param apiVersionInserter the inserter to use
 		 * @since 7.0
 		 */
-		Builder apiVersionInserter(ApiVersionInserter apiVersionInserter);
+		Builder apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter);
 
 		/**
 		 * Add the given filter to the filter chain.
diff --git a/spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClientBuilder.java b/spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClientBuilder.java
index c54170a4e9a..5957e345103 100644
--- a/spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClientBuilder.java
+++ b/spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClientBuilder.java
@@ -118,7 +118,7 @@ class DefaultRestTestClientBuilder<B extends RestTestClient.Builder<B>> implemen
 	}
 
 	@Override
-	public <T extends B> T apiVersionInserter(ApiVersionInserter apiVersionInserter) {
+	public <T extends B> T apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter) {
 		this.restClientBuilder.apiVersionInserter(apiVersionInserter);
 		return self();
 	}
diff --git a/spring-test/src/main/java/org/springframework/test/web/servlet/client/RestTestClient.java b/spring-test/src/main/java/org/springframework/test/web/servlet/client/RestTestClient.java
index 82b49bbd44e..1ed30c461b3 100644
--- a/spring-test/src/main/java/org/springframework/test/web/servlet/client/RestTestClient.java
+++ b/spring-test/src/main/java/org/springframework/test/web/servlet/client/RestTestClient.java
@@ -268,7 +268,7 @@ public interface RestTestClient {
 		 * of {@link ApiVersionInserter} for a list of choices.
 		 * @param apiVersionInserter the inserter to use
 		 */
-		<T extends B> T apiVersionInserter(ApiVersionInserter apiVersionInserter);
+		<T extends B> T apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter);
 
 		/**
 		 * Add the given request interceptor to the end of the interceptor chain.
diff --git a/spring-test/src/main/java/org/springframework/test/web/servlet/request/AbstractMockHttpServletRequestBuilder.java b/spring-test/src/main/java/org/springframework/test/web/servlet/request/AbstractMockHttpServletRequestBuilder.java
index f8caf80ab77..a08dda68a67 100644
--- a/spring-test/src/main/java/org/springframework/test/web/servlet/request/AbstractMockHttpServletRequestBuilder.java
+++ b/spring-test/src/main/java/org/springframework/test/web/servlet/request/AbstractMockHttpServletRequestBuilder.java
@@ -502,7 +502,7 @@ public abstract class AbstractMockHttpServletRequestBuilder<B extends AbstractMo
 	 * @param versionInserter the inserter to use
 	 * @since 7.0
 	 */
-	public B apiVersionInserter(ApiVersionInserter versionInserter) {
+	public B apiVersionInserter(@Nullable ApiVersionInserter versionInserter) {
 		this.versionInserter = versionInserter;
 		return self();
 	}
diff --git a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/AbstractMockMvcBuilder.java b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/AbstractMockMvcBuilder.java
index edba7107bdd..aa85262e979 100644
--- a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/AbstractMockMvcBuilder.java
+++ b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/AbstractMockMvcBuilder.java
@@ -111,7 +111,7 @@ public abstract class AbstractMockMvcBuilder<B extends AbstractMockMvcBuilder<B>
 	}
 
 	@Override
-	public <T extends B> T apiVersionInserter(ApiVersionInserter versionInserter) {
+	public <T extends B> T apiVersionInserter(@Nullable ApiVersionInserter versionInserter) {
 		this.apiVersionInserter = versionInserter;
 		return self();
 	}
diff --git a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java
index 50c946693c5..3f2defa0896 100644
--- a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java
+++ b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java
@@ -86,7 +86,7 @@ public interface ConfigurableMockMvcBuilder<B extends ConfigurableMockMvcBuilder
 	 * @param versionInserter the inserter to use
 	 * @since 7.0
 	 */
-	<T extends B> T apiVersionInserter(ApiVersionInserter versionInserter);
+	<T extends B> T apiVersionInserter(@Nullable ApiVersionInserter versionInserter);
 
 	/**
 	 * Define default request properties that should be merged into all
diff --git a/spring-web/src/main/java/org/springframework/web/client/DefaultRestClientBuilder.java b/spring-web/src/main/java/org/springframework/web/client/DefaultRestClientBuilder.java
index 1074838a637..94300c7fe1d 100644
--- a/spring-web/src/main/java/org/springframework/web/client/DefaultRestClientBuilder.java
+++ b/spring-web/src/main/java/org/springframework/web/client/DefaultRestClientBuilder.java
@@ -279,7 +279,7 @@ final class DefaultRestClientBuilder implements RestClient.Builder {
 	}
 
 	@Override
-	public RestClient.Builder apiVersionInserter(ApiVersionInserter apiVersionInserter) {
+	public RestClient.Builder apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter) {
 		this.apiVersionInserter = apiVersionInserter;
 		return this;
 	}
diff --git a/spring-web/src/main/java/org/springframework/web/client/RestClient.java b/spring-web/src/main/java/org/springframework/web/client/RestClient.java
index 27fc83c58cb..fd6075bb42f 100644
--- a/spring-web/src/main/java/org/springframework/web/client/RestClient.java
+++ b/spring-web/src/main/java/org/springframework/web/client/RestClient.java
@@ -353,7 +353,7 @@ public interface RestClient {
 		 * @param apiVersionInserter the inserter to use
 		 * @since 7.0
 		 */
-		Builder apiVersionInserter(ApiVersionInserter apiVersionInserter);
+		Builder apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter);
 
 		/**
 		 * Provide a consumer to customize every request being built.
diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java
index c6889d6f0be..bbab8fea18d 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java
@@ -205,7 +205,7 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 	}
 
 	@Override
-	public WebClient.Builder apiVersionInserter(ApiVersionInserter apiVersionInserter) {
+	public WebClient.Builder apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter) {
 		this.apiVersionInserter = apiVersionInserter;
 		return this;
 	}
diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClient.java b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClient.java
index 0a0dafbc77e..bf771443448 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClient.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClient.java
@@ -271,7 +271,7 @@ public interface WebClient {
 		 * @param apiVersionInserter the inserter to use
 		 * @since 7.0
 		 */
-		Builder apiVersionInserter(ApiVersionInserter apiVersionInserter);
+		Builder apiVersionInserter(@Nullable ApiVersionInserter apiVersionInserter);
 
 		/**
 		 * Provide a consumer to customize every request being built.