diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/MimeMappings.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/MimeMappings.java
index 077348af41c..e99968ece09 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/MimeMappings.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/MimeMappings.java
@@ -168,8 +168,8 @@ public sealed class MimeMappings implements Iterable<MimeMappings.Mapping> {
 	}
 
 	/**
-	 * Crate a new lazy copy of the given mappings will only copy entries if the mappings
-	 * are mutated.
+	 * Create a new lazy copy of the given mappings that will only copy entries if the
+	 * mappings are mutated.
 	 * @param mappings the source mappings
 	 * @return a new mappings instance
 	 * @since 3.0.0
@@ -349,7 +349,7 @@ public sealed class MimeMappings implements Iterable<MimeMappings.Mapping> {
 
 		private final MimeMappings source;
 
-		private AtomicBoolean copied = new AtomicBoolean();
+		private final AtomicBoolean copied = new AtomicBoolean();
 
 		LazyMimeMappingsCopy(MimeMappings source) {
 			this.source = source;
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java
index 9d8be88073a..aae9ebcbe9b 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java
@@ -181,7 +181,6 @@ class MimeMappingsTests {
 	void commonMappingsAreSubsetOfAllMappings() {
 		MimeMappings defaultMappings = new DefaultMimeMappings();
 		MimeMappings commonMappings = (MimeMappings) ReflectionTestUtils.getField(DefaultMimeMappings.class, "COMMON");
-		defaultMappings.getAll();
 		for (Mapping commonMapping : commonMappings) {
 			assertThat(defaultMappings.get(commonMapping.getExtension())).isEqualTo(commonMapping.getMimeType());
 		}
@@ -209,10 +208,11 @@ class MimeMappingsTests {
 		MimeMappings mappings = new MimeMappings();
 		mappings.add("json", "one/json");
 		MimeMappings lazyCopy = MimeMappings.lazyCopy(mappings);
+		lazyCopy.add("first", "copy/yes");
 		assertThat(lazyCopy.get("json")).isEqualTo("one/json");
 		mappings.add("json", "two/json");
-		lazyCopy.add("json", "other/json");
-		assertThat(lazyCopy.get("json")).isEqualTo("other/json");
+		lazyCopy.add("second", "copy/no");
+		assertThat(lazyCopy.get("json")).isEqualTo("one/json");
 	}
 
 	@Test