diff --git a/buffer/__init__.py b/buffer/__init__.py
index 5189e22..f00cc58 100644
--- a/buffer/__init__.py
+++ b/buffer/__init__.py
@@ -640,7 +640,8 @@ class FileBuffer(Buffer):
             f.close()
             self.store_checksum(data)
             data = self.read_filter(data)
-            self.codec = chardet.detect(data)['encoding'].lower()
+            codec = chardet.detect(data)['encoding'] or 'utf-8'
+            self.codec = codec.lower()
         else:
             data = ''
             self.codec = 'utf-8'