diff --git a/lib/xmet/series.py b/lib/xmet/series.py
index 5178f7b..7056936 100644
--- a/lib/xmet/series.py
+++ b/lib/xmet/series.py
@@ -47,7 +47,7 @@ class Series(dict):
             v1, v2 = self[pair[0]], series[pair[1]]
 
             if start is not None:
-                if pair[0] > start:
+                if pair[0] > start or pair[1] > start:
                     continue
 
             sign = SeriesIntersection.cmp(v1, v2)