diff --git a/natto/option_parse.py b/natto/option_parse.py
index b25007c..2f40157 100644
--- a/natto/option_parse.py
+++ b/natto/option_parse.py
@@ -76,7 +76,7 @@ def error(self, message):
         if type(options) is dict:
             for name in iter(list(self._SUPPORTED_OPTS.values())):
                 if name in options:
-                    if options[name]:
+                    if options[name] or options[name] is '':
                         val = options[name]
                         if isinstance(val, bytes):
                             val = self.__bytes2str(options[name])
@@ -148,12 +148,12 @@ def error(self, message):
                            help='set cost factor (default 700)',
                            action='store', dest='cost_factor', type=int)
 
-            opts = p.parse_args(options.split())
+            opts = p.parse_args([o.replace('\"', '').replace('\'', '') for o in options.split()])
 
             for name in iter(list(self._SUPPORTED_OPTS.values())):
                 if hasattr(opts, name):
                     v = getattr(opts, name)
-                    if v:
+                    if v or v is '':
                         dopts[name] = v
 
         # final checks