diff --git a/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatServerProperties.java b/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatServerProperties.java
index c895e25528d..224ea92ca3d 100644
--- a/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatServerProperties.java
+++ b/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatServerProperties.java
@@ -702,7 +702,7 @@ public class TomcatServerProperties {
 		/**
 		 * Time-to-live of the static resource cache.
 		 */
-		private @Nullable Duration cacheTtl;
+		private Duration cacheTtl = Duration.ofSeconds(5);
 
 		public boolean isAllowCaching() {
 			return this.allowCaching;
@@ -720,11 +720,11 @@ public class TomcatServerProperties {
 			this.cacheMaxSize = cacheMaxSize;
 		}
 
-		public @Nullable Duration getCacheTtl() {
+		public Duration getCacheTtl() {
 			return this.cacheTtl;
 		}
 
-		public void setCacheTtl(@Nullable Duration cacheTtl) {
+		public void setCacheTtl(Duration cacheTtl) {
 			this.cacheTtl = cacheTtl;
 		}
 
diff --git a/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizer.java b/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizer.java
index b067915ae70..79ed471fd4a 100644
--- a/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizer.java
+++ b/module/spring-boot-tomcat/src/main/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizer.java
@@ -380,12 +380,8 @@ public class TomcatWebServerFactoryCustomizer
 		factory.addContextCustomizers((context) -> context.addLifecycleListener((event) -> {
 			if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {
 				context.getResources().setCachingAllowed(resource.isAllowCaching());
-				long cacheMaxSize = resource.getCacheMaxSize().toKilobytes();
-				context.getResources().setCacheMaxSize(cacheMaxSize);
-				if (resource.getCacheTtl() != null) {
-					long ttl = resource.getCacheTtl().toMillis();
-					context.getResources().setCacheTtl(ttl);
-				}
+				context.getResources().setCacheMaxSize(resource.getCacheMaxSize().toKilobytes());
+				context.getResources().setCacheTtl(resource.getCacheTtl().toMillis());
 			}
 		}));
 	}
diff --git a/module/spring-boot-tomcat/src/test/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizerTests.java b/module/spring-boot-tomcat/src/test/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizerTests.java
index 8f9e9446db3..2aec1268555 100644
--- a/module/spring-boot-tomcat/src/test/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizerTests.java
+++ b/module/spring-boot-tomcat/src/test/java/org/springframework/boot/tomcat/autoconfigure/TomcatWebServerFactoryCustomizerTests.java
@@ -16,6 +16,7 @@
 
 package org.springframework.boot.tomcat.autoconfigure;
 
+import java.time.Duration;
 import java.util.Locale;
 import java.util.function.Consumer;
 
@@ -331,6 +332,8 @@ class TomcatWebServerFactoryCustomizerTests {
 			assertThat(properties.getResource().isAllowCaching()).isEqualTo(context.getResources().isCachingAllowed());
 			assertThat(properties.getResource().getCacheMaxSize())
 				.isEqualTo(DataSize.ofKilobytes(context.getResources().getCacheMaxSize()));
+			assertThat(properties.getResource().getCacheTtl())
+				.isEqualTo(Duration.ofMillis(context.getResources().getCacheTtl()));
 		});
 	}
 
@@ -356,7 +359,7 @@ class TomcatWebServerFactoryCustomizerTests {
 
 	@Test
 	void customStaticResourceCacheTtl() {
-		bind("server.tomcat.resource.cache-ttl=10000");
+		bind("server.tomcat.resource.cache-ttl=10s");
 		customizeAndRunServer((server) -> {
 			Tomcat tomcat = server.getTomcat();
 			Context context = (Context) tomcat.getHost().findChildren()[0];