15c82a
@@ -356,7 +356,9 @@
public class ProtobufHttpMessageConverter extends AbstractHttpMessageConverter<M
 				throws IOException {
 
 			if (contentType.isCompatibleWith(APPLICATION_JSON)) {
-				this.printer.appendTo(message, new OutputStreamWriter(output, charset));
+				OutputStreamWriter writer = new OutputStreamWriter(output, charset);
+				this.printer.appendTo(message, writer);
+				writer.flush();
 			}
 			else {
 				throw new IOException("protobuf-java-util does not support " + contentType + " format");
