diff --git a/src/main/java/gov/usgs/earthquake/nshmp/DisaggCalc.java b/src/main/java/gov/usgs/earthquake/nshmp/DisaggCalc.java
index 3af0e75d83302c1355680dd127c1c0d637eb2dd8..18f921924b73b3088745611c1a18c09bed39d143 100644
--- a/src/main/java/gov/usgs/earthquake/nshmp/DisaggCalc.java
+++ b/src/main/java/gov/usgs/earthquake/nshmp/DisaggCalc.java
@@ -517,12 +517,13 @@ public class DisaggCalc {
   }
 
   private static String disaggFilename(Site site) {
+    String baseName = String.format(
+        "%.2f,%.2f.csv",
+        site.location().longitude,
+        site.location().latitude);
     return site.name().equals(Site.NO_NAME)
-        ? String.format(
-            "%.2f,%.2f.json",
-            site.location().longitude,
-            site.location().latitude)
-        : site.name() + ".json";
+        ? baseName
+        : site.name() + "," + baseName;
   }
 
   private static final String PROGRAM = DisaggCalc.class.getSimpleName();