diff --git a/pystdf/IO.py b/pystdf/IO.py
index b1eb58a..4a9095c 100644
--- a/pystdf/IO.py
+++ b/pystdf/IO.py
@@ -236,7 +236,7 @@ def __init__(self, recTypes=V4.records, inp=sys.stdin, reopen_fn=None, endian=No
         for recType in recTypes ])
 
     self.vnMap = {
-      0: lambda header: self.inp.read(header, 1),
+      0: lambda header: self.inp.read(1),
       1: lambda header: self.readField(header, "U1"),
       2: lambda header: self.readField(header, "U2"),
       3: lambda header: self.readField(header, "U4"),