diff --git a/src/main/java/gov/usgs/earthquake/nshmp/data/Sequences.java b/src/main/java/gov/usgs/earthquake/nshmp/data/Sequences.java
index bc3c896de1f70436a5a66a0bf4f5828b501bcee1..2a131359cb3691d3d9d7e751cb24f49c559bf07f 100644
--- a/src/main/java/gov/usgs/earthquake/nshmp/data/Sequences.java
+++ b/src/main/java/gov/usgs/earthquake/nshmp/data/Sequences.java
@@ -103,7 +103,7 @@ class Sequences {
         .flatMap(XySequence::stream)
         .collect(Collectors.toMap(
             XyPoint::x,
-            (XyPoint xy) -> (double) xy.y(),
+            XyPoint::y,
             Double::sum,
             TreeMap::new));
     return XySequence.create(