diff --git a/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartHttpMessageWriter.java b/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartHttpMessageWriter.java
index 50e9a264d1a..d94104535d1 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartHttpMessageWriter.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartHttpMessageWriter.java
@@ -16,7 +16,6 @@
 
 package org.springframework.http.codec.multipart;
 
-import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -146,17 +145,6 @@ public class MultipartHttpMessageWriter extends MultipartWriterSupport
 		return this.formWriter;
 	}
 
-	/**
-	 * Set the character set to use for part headers such as
-	 * "Content-Disposition" (and its filename parameter).
-	 * <p>By default this is set to "UTF-8". If changed from this default,
-	 * the "Content-Type" header will have a "charset" parameter that specifies
-	 * the character set used.
-	 */
-	public void setCharset(Charset charset) {
-		Assert.notNull(charset, "Charset must not be null");
-		this.charset = charset;
-	}
 
 
 	@Override
diff --git a/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartWriterSupport.java b/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartWriterSupport.java
index 0ddae070e04..b07eb720a56 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartWriterSupport.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartWriterSupport.java
@@ -30,6 +30,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.LoggingCodecSupport;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.MimeTypeUtils;
 import org.springframework.util.MultiValueMap;
 
@@ -44,9 +45,9 @@ public class MultipartWriterSupport extends LoggingCodecSupport {
 	/** THe default charset used by the writer. */
 	public static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;
 
-	protected final List<MediaType> supportedMediaTypes;
+	private final List<MediaType> supportedMediaTypes;
 
-	protected Charset charset = DEFAULT_CHARSET;
+	private Charset charset = DEFAULT_CHARSET;
 
 
 	/**
@@ -64,6 +65,18 @@ public class MultipartWriterSupport extends LoggingCodecSupport {
 		return this.charset;
 	}
 
+	/**
+	 * Set the character set to use for part headers such as
+	 * "Content-Disposition" (and its filename parameter).
+	 * <p>By default this is set to "UTF-8". If changed from this default,
+	 * the "Content-Type" header will have a "charset" parameter that specifies
+	 * the character set used.
+	 */
+	public void setCharset(Charset charset) {
+		Assert.notNull(charset, "Charset must not be null");
+		this.charset = charset;
+	}
+
 	public List<MediaType> getWritableMediaTypes() {
 		return this.supportedMediaTypes;
 	}