diff --git a/src/main/java/li/cil/oc/server/fs/Capacity.scala b/src/main/java/li/cil/oc/server/fs/Capacity.scala
index f0a9d2fdd..3e39e005b 100644
--- a/src/main/java/li/cil/oc/server/fs/Capacity.scala
+++ b/src/main/java/li/cil/oc/server/fs/Capacity.scala
@@ -78,6 +78,9 @@ trait Capacity extends OutputStreamFileSystem {
       case None => None
       case Some(stream) =>
         used += delta
+        if (mode == Mode.Append) {
+          stream.seek(stream.length())
+        }
         Some(new CountingOutputHandle(this, stream))
     }
   }
diff --git a/src/main/java/li/cil/oc/server/fs/FileOutputStreamFileSystem.scala b/src/main/java/li/cil/oc/server/fs/FileOutputStreamFileSystem.scala
index 0e43ddc0f..de1eaa9a6 100644
--- a/src/main/java/li/cil/oc/server/fs/FileOutputStreamFileSystem.scala
+++ b/src/main/java/li/cil/oc/server/fs/FileOutputStreamFileSystem.scala
@@ -23,8 +23,7 @@ trait FileOutputStreamFileSystem extends FileInputStreamFileSystem with OutputSt
 
   override protected def openOutputHandle(id: Int, path: String, mode: Mode): Option[OutputHandle] =
     Some(new FileHandle(new RandomAccessFile(new io.File(root, path), mode match {
-      case Mode.Append => "a"
-      case Mode.Write => "w"
+      case Mode.Append | Mode.Write => "rw"
       case _ => throw new IllegalArgumentException()
     }), this, id, path))