diff --git a/vdirsyncer/storage/filesystem.py b/vdirsyncer/storage/filesystem.py
index cbfebe1..bf29d3f 100644
--- a/vdirsyncer/storage/filesystem.py
+++ b/vdirsyncer/storage/filesystem.py
@@ -116,7 +116,7 @@ class FilesystemStorage(Storage):
             fpath, etag = self._upload_impl(item, href)
         except OSError as e:
             if e.errno in (errno.ENAMETOOLONG, errno.ENOENT):  # Unix  # Windows
-                logger.debug("UID as filename rejected, trying with random " "one.")
+                logger.debug("UID as filename rejected, trying with random one.")
                 # random href instead of UID-based
                 href = self._get_href(None)
                 fpath, etag = self._upload_impl(item, href)
diff --git a/vdirsyncer/utils.py b/vdirsyncer/utils.py
index 33cd7d1..af66eb7 100644
--- a/vdirsyncer/utils.py
+++ b/vdirsyncer/utils.py
@@ -11,9 +11,7 @@ from . import exceptions
 # not included, because there are some servers that (incorrectly) encode it to
 # `%40` when it's part of a URL path, and reject or "repair" URLs that contain
 # `@` in the path. So it's better to just avoid it.
-SAFE_UID_CHARS = (
-    "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "0123456789_.-+"
-)
+SAFE_UID_CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_.-+"
 
 
 _missing = object()