diff --git a/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringDecoder.java b/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringDecoder.java
index 684df592298..2529a81997a 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringDecoder.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringDecoder.java
@@ -102,7 +102,7 @@ public abstract class KotlinSerializationStringDecoder<T extends StringFormat> e
 
 	@Override
 	public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
-		return canSerialize(elementType, mimeType);
+		return canSerialize(elementType, mimeType) && !CharSequence.class.isAssignableFrom(elementType.toClass());
 	}
 
 	@Override
diff --git a/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringEncoder.java b/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringEncoder.java
index 18d7330b453..c9046bee552 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringEncoder.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationStringEncoder.java
@@ -101,7 +101,7 @@ public abstract class KotlinSerializationStringEncoder<T extends StringFormat> e
 
 	@Override
 	public boolean canEncode(ResolvableType elementType, @Nullable MimeType mimeType) {
-		return canSerialize(elementType, mimeType);
+		return canSerialize(elementType, mimeType) && !String.class.isAssignableFrom(elementType.toClass());
 	}
 
 	@Override
diff --git a/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationSupport.java b/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationSupport.java
index 1d144926c0a..b69dae1253a 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationSupport.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/KotlinSerializationSupport.java
@@ -117,7 +117,7 @@ public abstract class KotlinSerializationSupport<T extends SerialFormat> {
 		if (!this.typePredicate.test(type) || ResolvableType.NONE.equals(type)) {
 			return false;
 		}
-		return serializer(type) != null && supports(mimeType);
+		return serializer(type) != null && supports(mimeType) && !ServerSentEvent.class.isAssignableFrom(type.toClass());
 	}
 
 	private boolean supports(@Nullable MimeType mimeType) {
diff --git a/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonDecoderTests.kt b/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonDecoderTests.kt
index 10689531892..28c8f87ec5b 100644
--- a/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonDecoderTests.kt
+++ b/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonDecoderTests.kt
@@ -80,7 +80,7 @@ class KotlinSerializationJsonDecoderTests : AbstractDecoderTests<KotlinSerializa
 		assertThat(decoderForAllTypes.canDecode(ResolvableType.forClass(Pojo::class.java), MediaType.APPLICATION_JSON)).isTrue()
 		assertThat(decoderForAllTypes.canDecode(ResolvableType.forClass(Pojo::class.java), jsonSubtype)).isTrue()
 		assertThat(decoderForAllTypes.canDecode(ResolvableType.forClass(Pojo::class.java), null)).isTrue()
-		assertThat(decoderForAllTypes.canDecode(ResolvableType.forClass(String::class.java), null)).isTrue()
+		assertThat(decoderForAllTypes.canDecode(ResolvableType.forClass(String::class.java), null)).isFalse()
 		assertThat(decoderForAllTypes.canDecode(ResolvableType.forClass(Pojo::class.java), MediaType.APPLICATION_XML)).isFalse()
 		assertThat(decoderForAllTypes.canDecode(ResolvableType.forClass(Pojo::class.java),
 			MediaType("application", "json", StandardCharsets.UTF_8))).isTrue()
diff --git a/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonEncoderTests.kt b/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonEncoderTests.kt
index 9da09e3bdac..59bf4c71131 100644
--- a/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonEncoderTests.kt
+++ b/spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonEncoderTests.kt
@@ -91,7 +91,7 @@ class KotlinSerializationJsonEncoderTests : AbstractEncoderTests<KotlinSerializa
 
 		assertThat(encoderForAllTypes.canEncode(pojoType, MediaType.APPLICATION_NDJSON)).isTrue()
 
-		assertThat(encoderForAllTypes.canEncode(ResolvableType.forClass(String::class.java), null)).isTrue()
+		assertThat(encoderForAllTypes.canEncode(ResolvableType.forClass(String::class.java), null)).isFalse()
 		assertThat(encoderForAllTypes.canEncode(ResolvableType.forClass(Pojo::class.java), MediaType.APPLICATION_XML)).isFalse()
 		val sseType = ResolvableType.forClass(ServerSentEvent::class.java)
 		assertThat(encoderForAllTypes.canEncode(sseType, MediaType.APPLICATION_JSON)).isFalse()