diff --git a/CHANGES.txt b/CHANGES.txt
index 020b523..37ff25c 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -12,6 +12,9 @@
 
   BUG FIXES
 
+    AVRO-1741: Python3: Fix error when codec is not in the header.
+    (Matthew Hayes via blue)
+
 Avro 1.8.1 (14 May 2016)
 
   INCOMPATIBLE CHANGES
diff --git a/lang/py3/avro/datafile.py b/lang/py3/avro/datafile.py
index fc93fe1..7894d79 100644
--- a/lang/py3/avro/datafile.py
+++ b/lang/py3/avro/datafile.py
@@ -349,9 +349,11 @@
     self._read_header()
 
     # ensure codec is valid
-    self.codec = self.GetMeta('avro.codec').decode('utf-8')
-    if self.codec is None:
+    avro_codec_raw = self.GetMeta('avro.codec')
+    if avro_codec_raw is None:
       self.codec = "null"
+    else:
+      self.codec = avro_codec_raw.decode('utf-8')
     if self.codec not in VALID_CODECS:
       raise DataFileException('Unknown codec: %s.' % self.codec)