diff --git a/ox/cache.py b/ox/cache.py
index 4137a36..123ec96 100644
--- a/ox/cache.py
+++ b/ox/cache.py
@@ -119,9 +119,8 @@ def save_url(url, filename, overwrite=False):
         if not os.path.exists(dirname):
             os.makedirs(dirname)
         data = read_url(url)
-        f = open(filename, 'w')
-        f.write(data)
-        f.close()
+        with open(filename, 'wb') as f:
+            f.write(data)
 
 def cache_path():
     return os.environ.get('oxCACHE', os.path.expanduser('~/.ox/cache'))
@@ -292,7 +291,7 @@ class FileCache(Cache):
                 if value == 'headers':
                     r = info['headers']
                 else:
-                    with open(f) as data:
+                    with open(f, 'rb') as data:
                         r = data.read()
                     if info['compressed']:
                         r = zlib.decompress(r)
@@ -323,9 +322,11 @@ class FileCache(Cache):
         if not info['only_headers']:
             if info['compressed']:
                 data = zlib.compress(data)
-            with open(f, 'w') as _f:
+            elif not isinstance(data, str):
+                data = data.encode('utf-8')
+            with open(f, 'wb') as _f:
                 _f.write(data)
-        with open(i, 'w') as _i:
+        with open(i, 'wb') as _i:
             json.dump(info, _i)
 
 if cache_path().startswith('fs:'):