diff --git a/mobi/mobi_dict.py b/mobi/mobi_dict.py
index bf4bb86..b00193c 100644
--- a/mobi/mobi_dict.py
+++ b/mobi/mobi_dict.py
@@ -422,4 +422,4 @@ def applyInflectionRule(self, mainEntry, inflectionRuleData, start, end):
             else:
                 logger.debug("Error: Inflection rule mode %x is not implemented" % abyte)
                 return None
-        return utf8_str(byteArray.tostring())
+        return utf8_str(byteArray.tobytes())