diff --git a/ocat b/ocat
index 73621ad1..802d3c22 100755
Binary files a/ocat and b/ocat differ
diff --git a/showdef b/showdef
index f29f352c..425e4c63 100755
Binary files a/showdef and b/showdef differ
diff --git a/src/lib/v4/OakFiles.Mod b/src/lib/v4/OakFiles.Mod
index 9a20afd8..d52d5947 100644
--- a/src/lib/v4/OakFiles.Mod
+++ b/src/lib/v4/OakFiles.Mod
@@ -427,6 +427,18 @@ BEGIN
   buf.data[offset] := x; r.offset := offset + 1; buf.chg := TRUE
 END Write;
 
+PROCEDURE WriteByte* (VAR r: Rider; x: SYSTEM.BYTE); (* added for compatibility with PO 2013, -- noch *)
+  VAR buf: Buffer; offset: LONGINT;
+BEGIN
+  buf := r.buf; offset := r.offset;
+  IF (offset >= bufsize) OR (r.org # buf.org) THEN 
+    Set(r, buf.f, r.org + offset); buf := r.buf; offset := r.offset;
+  END ;
+  buf.data[offset] := x; r.offset := offset + 1; buf.chg := TRUE
+END Write;
+
+
+
 PROCEDURE WriteBytes ...
 
 PROCEDURE Read* (VAR r: Rider; VAR x: SYSTEM.BYTE);
diff --git a/voc b/voc
index 61878042..886580f2 100755
Binary files a/voc and b/voc differ