diff --git a/lib/xmet/series.py b/lib/xmet/series.py
index 64ac90a..d8c7e12 100644
--- a/lib/xmet/series.py
+++ b/lib/xmet/series.py
@@ -25,7 +25,10 @@ class Series(dict):
         return nearest(sorted(self.keys(),   reverse=True),
                        sorted(series.keys(), reverse=True))
 
-    def intersect(self, series: Self, intersection: SeriesIntersection, start: float=None) -> tuple[float]:
+    def intersect(self,
+                  series: Self,
+                  intersection: SeriesIntersection,
+                  start: float=None) -> tuple[float]:
         pairs = self.neighbors(series)
 
         for pair in pairs: