diff --git a/spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java b/spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java
index ced2ae1767f..76496f58329 100644
--- a/spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java
+++ b/spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java
@@ -384,7 +384,7 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 	private void writeForm(MultiValueMap<String, Object> formData, @Nullable MediaType contentType,
 			HttpOutputMessage outputMessage) throws IOException {
 
-		contentType = getMediaType(contentType);
+		contentType = getFormContentType(contentType);
 		outputMessage.getHeaders().setContentType(contentType);
 
 		Charset charset = contentType.getCharset();
@@ -402,15 +402,27 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 		}
 	}
 
-	private MediaType getMediaType(@Nullable MediaType mediaType) {
-		if (mediaType == null) {
+	/**
+	 * Return the content type used to write forms, given the preferred content type.
+	 * By default, this method returns the given content type, but adds the
+	 * {@linkplain #setCharset(Charset) charset} if it does not have one.
+	 * If {@code contentType} is {@code null},
+	 * {@code application/x-www-form-urlencoded; charset=UTF-8} is returned.
+	 *
+	 * <p>Subclasses can override this method to change this behavior.
+	 * @param contentType the preferred content type, can be {@code null}
+	 * @return the content type to be used
+	 * @since 5.2.2
+	 */
+	protected MediaType getFormContentType(@Nullable MediaType contentType) {
+		if (contentType == null) {
 			return DEFAULT_FORM_DATA_MEDIA_TYPE;
 		}
-		else if (mediaType.getCharset() == null) {
-			return new MediaType(mediaType, this.charset);
+		else if (contentType.getCharset() == null) {
+			return new MediaType(contentType, this.charset);
 		}
 		else {
-			return mediaType;
+			return contentType;
 		}
 	}