diff --git a/crawl.py b/crawl.py
index 3b44654..64cb332 100755
--- a/crawl.py
+++ b/crawl.py
@@ -52,6 +52,7 @@ parser.add_argument(
 parser.add_argument(
     '--cache-dir',
     dest='cache_dir',
+    type=str,
     help='Override the default cache directory with your own path'
 )
 exc_group = parser.add_mutually_exclusive_group()
@@ -78,23 +79,23 @@ vals_group.add_argument(
 
 
 def _process_stdin(argv: str, res: utils.CurrencyResult) -> None:
-    argv=argv.split()
+    argv = argv.split()
     try:
         if argv[0] in ['q', 'exit', 'quit']:
             sys.exit()
         elif argv[0] in ['date', 'd']:
             print(res.date)
-        elif len(argv[0])==3 or len(argv[1])==3:
+        elif len(argv[0]) == 3 or len(argv[1]) == 3:
             # more than 3 letter abbreviations are invalid
             if is_float(argv[0]):
-                # amount first -> convert to currency in argv[1] 
+                # amount first -> convert to currency in argv[1]
                 print(fmt_and_calc(
                     cur=argv[1].upper(),
                     amt=float(argv[0]),
                     res=res,
                     direction=DIRECTION_FROM_EUR))
             elif is_float(argv[1]):
-                # currency first -> convert to EUR 
+                # currency first -> convert to EUR
                 print(fmt_and_calc(
                     cur=argv[0].upper(),
                     amt=float(argv[1]),