diff --git a/io/src/main/scala/sbt/io/IO.scala b/io/src/main/scala/sbt/io/IO.scala
index 42585017..8a1cae9f 100644
--- a/io/src/main/scala/sbt/io/IO.scala
+++ b/io/src/main/scala/sbt/io/IO.scala
@@ -767,7 +767,7 @@ object IO {
             os.closeEntry()
 
             (os, "jar")
-          case None => (new ZipOutputStream(fileOut), "zip")
+          case None => (new ZipOutputStream(fileOut, defaultCharset), "zip")
         }
       try {
         f(zipOut)