diff --git a/spring-web/src/testFixtures/java/org/springframework/web/testfixture/http/server/reactive/MockServerHttpResponse.java b/spring-web/src/testFixtures/java/org/springframework/web/testfixture/http/server/reactive/MockServerHttpResponse.java
index 14ae615f10..6b69119ea3 100644
--- a/spring-web/src/testFixtures/java/org/springframework/web/testfixture/http/server/reactive/MockServerHttpResponse.java
+++ b/spring-web/src/testFixtures/java/org/springframework/web/testfixture/http/server/reactive/MockServerHttpResponse.java
@@ -26,6 +26,7 @@ import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.core.publisher.MonoProcessor;
+import reactor.core.publisher.Sinks;
 
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
@@ -64,7 +65,7 @@ public class MockServerHttpResponse extends AbstractServerHttpResponse {
 		super(dataBufferFactory);
 		this.writeHandler = body -> {
 			// Avoid .then() which causes data buffers to be released
-			MonoProcessor<Void> completion = MonoProcessor.create();
+			MonoProcessor<Void> completion = MonoProcessor.fromSink(Sinks.one());
 			this.body = body.doOnComplete(completion::onComplete).doOnError(completion::onError).cache();
 			this.body.subscribe();
 			return completion;