diff --git a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfiguration.java b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfiguration.java
index af302e459de..722c5706f31 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfiguration.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfiguration.java
@@ -62,7 +62,7 @@ public class ReactiveMultipartAutoConfiguration {
 					.asInt(DataSize::toBytes)
 					.to(defaultPartHttpMessageReader::setMaxHeadersSize);
 				map.from(multipartProperties::getMaxDiskUsagePerPart)
-					.asInt(DataSize::toBytes)
+					.as(DataSize::toBytes)
 					.to(defaultPartHttpMessageReader::setMaxDiskUsagePerPart);
 				map.from(multipartProperties::getMaxParts).to(defaultPartHttpMessageReader::setMaxParts);
 				map.from(multipartProperties::getFileStorageDirectory)
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfigurationTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfigurationTests.java
index ccbc01ae7bb..d5925346e13 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfigurationTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfigurationTests.java
@@ -62,7 +62,7 @@ class ReactiveMultipartAutoConfigurationTests {
 		this.contextRunner
 			.withPropertyValues("spring.webflux.multipart.max-in-memory-size=1GB",
 					"spring.webflux.multipart.max-headers-size=16KB",
-					"spring.webflux.multipart.max-disk-usage-per-part=100MB", "spring.webflux.multipart.max-parts=7",
+					"spring.webflux.multipart.max-disk-usage-per-part=3GB", "spring.webflux.multipart.max-parts=7",
 					"spring.webflux.multipart.headers-charset:UTF_16")
 			.run((context) -> {
 				CodecCustomizer customizer = context.getBean(CodecCustomizer.class);
@@ -76,7 +76,7 @@ class ReactiveMultipartAutoConfigurationTests {
 				assertThat(partReader).hasFieldOrPropertyWithValue("maxInMemorySize",
 						Math.toIntExact(DataSize.ofGigabytes(1).toBytes()));
 				assertThat(partReader).hasFieldOrPropertyWithValue("maxDiskUsagePerPart",
-						DataSize.ofMegabytes(100).toBytes());
+						DataSize.ofGigabytes(3).toBytes());
 			});
 	}