diff --git a/spring-web/src/main/java/org/springframework/web/accept/DefaultApiVersionStrategy.java b/spring-web/src/main/java/org/springframework/web/accept/DefaultApiVersionStrategy.java
index ab92cbb0561..2e29b9d8ae6 100644
--- a/spring-web/src/main/java/org/springframework/web/accept/DefaultApiVersionStrategy.java
+++ b/spring-web/src/main/java/org/springframework/web/accept/DefaultApiVersionStrategy.java
@@ -90,6 +90,10 @@ public class DefaultApiVersionStrategy implements ApiVersionStrategy {
 		this.detectSupportedVersions = detectSupportedVersions;
 		this.supportedVersionPredicate = initSupportedVersionPredicate(supportedVersionPredicate);
 		this.deprecationHandler = deprecationHandler;
+
+		if (defaultVersion != null) {
+			addSupportedVersion(defaultVersion);
+		}
 	}
 
 	private Predicate<Comparable<?>> initSupportedVersionPredicate(@Nullable Predicate<Comparable<?>> predicate) {
diff --git a/spring-web/src/test/java/org/springframework/web/accept/DefaultApiVersionStrategiesTests.java b/spring-web/src/test/java/org/springframework/web/accept/DefaultApiVersionStrategiesTests.java
index be1597479f9..4bf44c79374 100644
--- a/spring-web/src/test/java/org/springframework/web/accept/DefaultApiVersionStrategiesTests.java
+++ b/spring-web/src/test/java/org/springframework/web/accept/DefaultApiVersionStrategiesTests.java
@@ -46,7 +46,7 @@ public class DefaultApiVersionStrategiesTests {
 
 	@Test
 	void missingRequiredVersion() {
-		assertThatThrownBy(() -> validateVersion(null, apiVersionStrategy()))
+		assertThatThrownBy(() -> testValidate(null, apiVersionStrategy()))
 				.isInstanceOf(MissingApiVersionException.class)
 				.hasMessage("400 BAD_REQUEST \"API version is required.\"");
 	}
@@ -56,12 +56,19 @@ public class DefaultApiVersionStrategiesTests {
 		String version = "1.2";
 		DefaultApiVersionStrategy strategy = apiVersionStrategy();
 		strategy.addSupportedVersion(version);
-		validateVersion(version, strategy);
+		testValidate(version, strategy);
+	}
+
+	@Test
+	void validateSupportedVersionForDefaultVersion() {
+		String defaultVersion = "1.2";
+		DefaultApiVersionStrategy strategy = apiVersionStrategy(defaultVersion);
+		testValidate(defaultVersion, strategy);
 	}
 
 	@Test
 	void validateUnsupportedVersion() {
-		assertThatThrownBy(() -> validateVersion("1.2", apiVersionStrategy()))
+		assertThatThrownBy(() -> testValidate("1.2", apiVersionStrategy()))
 				.isInstanceOf(InvalidApiVersionException.class)
 				.hasMessage("400 BAD_REQUEST \"Invalid API version: '1.2.0'.\"");
 	}
@@ -71,7 +78,7 @@ public class DefaultApiVersionStrategiesTests {
 		String version = "1.2";
 		DefaultApiVersionStrategy strategy = apiVersionStrategy(null, true, null);
 		strategy.addMappedVersion(version);
-		validateVersion(version, strategy);
+		testValidate(version, strategy);
 	}
 
 	@Test
@@ -79,19 +86,19 @@ public class DefaultApiVersionStrategiesTests {
 		String version = "1.2";
 		DefaultApiVersionStrategy strategy = apiVersionStrategy();
 		strategy.addMappedVersion(version);
-		assertThatThrownBy(() -> validateVersion(version, strategy)).isInstanceOf(InvalidApiVersionException.class);
+		assertThatThrownBy(() -> testValidate(version, strategy)).isInstanceOf(InvalidApiVersionException.class);
 	}
 
 	@Test
 	void validateSupportedWithPredicate() {
 		SemanticApiVersionParser.Version parsedVersion = parser.parseVersion("1.2");
-		validateVersion("1.2", apiVersionStrategy(null, false, version -> version.equals(parsedVersion)));
+		testValidate("1.2", apiVersionStrategy(null, false, version -> version.equals(parsedVersion)));
 	}
 
 	@Test
 	void validateUnsupportedWithPredicate() {
 		DefaultApiVersionStrategy strategy = apiVersionStrategy(null, false, version -> version.equals("1.2"));
-		assertThatThrownBy(() -> validateVersion("1.2", strategy)).isInstanceOf(InvalidApiVersionException.class);
+		assertThatThrownBy(() -> testValidate("1.2", strategy)).isInstanceOf(InvalidApiVersionException.class);
 	}
 
 	@Test
@@ -121,7 +128,7 @@ public class DefaultApiVersionStrategiesTests {
 				null, defaultVersion, detectSupportedVersions, supportedVersionPredicate, null);
 	}
 
-	private void validateVersion(@Nullable String version, DefaultApiVersionStrategy strategy) {
+	private void testValidate(@Nullable String version, DefaultApiVersionStrategy strategy) {
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		if (version != null) {
 			request.setParameter("api-version", version);
diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategy.java b/spring-webflux/src/main/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategy.java
index d2dac706b69..da641e2e14b 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategy.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategy.java
@@ -92,6 +92,10 @@ public class DefaultApiVersionStrategy implements ApiVersionStrategy {
 		this.detectSupportedVersions = detectSupportedVersions;
 		this.supportedVersionPredicate = initSupportedVersionPredicate(supportedVersionPredicate);
 		this.deprecationHandler = deprecationHandler;
+
+		if (defaultVersion != null) {
+			addSupportedVersion(defaultVersion);
+		}
 	}
 
 	private Predicate<Comparable<?>> initSupportedVersionPredicate(@Nullable Predicate<Comparable<?>> predicate) {
diff --git a/spring-webflux/src/test/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategiesTests.java b/spring-webflux/src/test/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategiesTests.java
index 377cc2f8704..1b46a2bbb0a 100644
--- a/spring-webflux/src/test/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategiesTests.java
+++ b/spring-webflux/src/test/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategiesTests.java
@@ -50,7 +50,7 @@ public class DefaultApiVersionStrategiesTests {
 
 	@Test
 	void missingRequiredVersion() {
-		assertThatThrownBy(() -> validateVersion(null, apiVersionStrategy()))
+		assertThatThrownBy(() -> testValidate(null, apiVersionStrategy()))
 				.isInstanceOf(MissingApiVersionException.class)
 				.hasMessage("400 BAD_REQUEST \"API version is required.\"");
 	}
@@ -60,12 +60,19 @@ public class DefaultApiVersionStrategiesTests {
 		String version = "1.2";
 		DefaultApiVersionStrategy strategy = apiVersionStrategy();
 		strategy.addSupportedVersion(version);
-		validateVersion(version, strategy);
+		testValidate(version, strategy);
+	}
+
+	@Test
+	void validateSupportedVersionForDefaultVersion() {
+		String defaultVersion = "1.2";
+		DefaultApiVersionStrategy strategy = apiVersionStrategy(defaultVersion, false, null);
+		testValidate(defaultVersion, strategy);
 	}
 
 	@Test
 	void validateUnsupportedVersion() {
-		assertThatThrownBy(() -> validateVersion("1.2", apiVersionStrategy()))
+		assertThatThrownBy(() -> testValidate("1.2", apiVersionStrategy()))
 				.isInstanceOf(InvalidApiVersionException.class)
 				.hasMessage("400 BAD_REQUEST \"Invalid API version: '1.2.0'.\"");
 	}
@@ -75,7 +82,7 @@ public class DefaultApiVersionStrategiesTests {
 		String version = "1.2";
 		DefaultApiVersionStrategy strategy = apiVersionStrategy(null, true, null);
 		strategy.addMappedVersion(version);
-		validateVersion(version, strategy);
+		testValidate(version, strategy);
 	}
 
 	@Test
@@ -83,19 +90,19 @@ public class DefaultApiVersionStrategiesTests {
 		String version = "1.2";
 		DefaultApiVersionStrategy strategy = apiVersionStrategy();
 		strategy.addMappedVersion(version);
-		assertThatThrownBy(() -> validateVersion(version, strategy)).isInstanceOf(InvalidApiVersionException.class);
+		assertThatThrownBy(() -> testValidate(version, strategy)).isInstanceOf(InvalidApiVersionException.class);
 	}
 
 	@Test
 	void validateSupportedWithPredicate() {
 		SemanticApiVersionParser.Version parsedVersion = parser.parseVersion("1.2");
-		validateVersion("1.2", apiVersionStrategy(null, false, version -> version.equals(parsedVersion)));
+		testValidate("1.2", apiVersionStrategy(null, false, version -> version.equals(parsedVersion)));
 	}
 
 	@Test
 	void validateUnsupportedWithPredicate() {
 		DefaultApiVersionStrategy strategy = apiVersionStrategy(null, false, version -> version.equals("1.2"));
-		assertThatThrownBy(() -> validateVersion("1.2", strategy)).isInstanceOf(InvalidApiVersionException.class);
+		assertThatThrownBy(() -> testValidate("1.2", strategy)).isInstanceOf(InvalidApiVersionException.class);
 	}
 
 	@Test
@@ -121,7 +128,7 @@ public class DefaultApiVersionStrategiesTests {
 				parser, null, defaultVersion, detectSupportedVersions, supportedVersionPredicate, null);
 	}
 
-	private void validateVersion(@Nullable String version, DefaultApiVersionStrategy strategy) {
+	private void testValidate(@Nullable String version, DefaultApiVersionStrategy strategy) {
 		MockServerHttpRequest.BaseBuilder<?> requestBuilder = MockServerHttpRequest.get("/");
 		if (version != null) {
 			requestBuilder.queryParam("api-version", version);