diff --git a/src/whitenoise/middleware.py b/src/whitenoise/middleware.py
index 095a2d98..3cb5f499 100644
--- a/src/whitenoise/middleware.py
+++ b/src/whitenoise/middleware.py
@@ -96,7 +96,7 @@ def __init__(self, get_response=None, settings=settings):
             if settings.FORCE_SCRIPT_NAME:
                 script_name = settings.FORCE_SCRIPT_NAME.rstrip("/")
                 if self.static_prefix.startswith(script_name):
-                    self.static_prefix = self.static_prefix[len(script_name):]
+                    self.static_prefix = self.static_prefix[len(script_name) :]
         self.static_prefix = ensure_leading_trailing_slash(self.static_prefix)
 
         self.static_root = settings.STATIC_ROOT