diff --git a/vendor/golang.org/x/net/internal/timeseries/timeseries.go b/vendor/golang.org/x/net/internal/timeseries/timeseries.go
index 685f0e7..dc5225b 100644
--- a/vendor/golang.org/x/net/internal/timeseries/timeseries.go
+++ b/vendor/golang.org/x/net/internal/timeseries/timeseries.go
@@ -403,9 +403,9 @@
 
 	// Where should scanning start?
 	if dstStart.After(srcStart) {
-		advance := dstStart.Sub(srcStart) / srcInterval
-		srcIndex += int(advance)
-		srcStart = srcStart.Add(advance * srcInterval)
+		advance := int(dstStart.Sub(srcStart) / srcInterval)
+		srcIndex += advance
+		srcStart = srcStart.Add(time.Duration(advance) * srcInterval)
 	}
 
 	// The i'th value is computed as show below.