diff --git a/bin/sassw b/bin/sassw
index af1c693..949ee83 100755
--- a/bin/sassw
+++ b/bin/sassw
@@ -22,31 +22,41 @@ if os.path.isdir(filename):
 else:
     filenames = sys.argv[1:]
 
+
 def build():
     global sources, directories
     directories = set()
     sources = set()
     for filename in filenames:
         result = subprocess.run(
-                ['sassc', '-mauto', filename, filename.replace('.scss', '.css')],
-                capture_output=True,
-                text=True)
+            ['sassc', '-mauto', filename, filename.replace('.scss', '.css')], capture_output=True, text=True
+        )
         sys.stdout.write(result.stdout)
         sys.stderr.write(result.stderr)
         if result.returncode:
             # error
             with open(filename.replace('.scss', '.css'), 'w') as fd:
-                print('''body::before {
+                print(
+                    '''body::before {
                           white-space: pre;
                           font-family: monospace;
                           content: "%s";
-                         }''' % result.stderr.replace('\n', '\\A').replace('"', '\\"'),
-                    file=fd)
+                         }'''
+                    % result.stderr.replace('\n', '\\A').replace('"', '\\"'),
+                    file=fd,
+                )
         basepath = os.path.abspath(os.path.dirname(filename))
-        sources = sources.union(set([os.path.abspath(os.path.join(basepath, x))
-            for x in json.load(open(filename.replace('.scss', '.css.map')))['sources']]))
+        sources = sources.union(
+            set(
+                [
+                    os.path.abspath(os.path.join(basepath, x))
+                    for x in json.load(open(filename.replace('.scss', '.css.map')))['sources']
+                ]
+            )
+        )
         directories = directories.union(set([os.path.dirname(x) for x in sources]))
 
+
 class EventManager(pyinotify.ProcessEvent):
     def process_default(self, event):
         if event.pathname in sources: