diff --git a/src/main/java/gov/usgs/earthquake/nshmp/gmm/GroundMotions.java b/src/main/java/gov/usgs/earthquake/nshmp/gmm/GroundMotions.java
index 21859e005053ba55078fc7a2fa042b8148be85d4..db30dd33d293e535494f761b27648fe256bfe33e 100644
--- a/src/main/java/gov/usgs/earthquake/nshmp/gmm/GroundMotions.java
+++ b/src/main/java/gov/usgs/earthquake/nshmp/gmm/GroundMotions.java
@@ -32,7 +32,7 @@ class GroundMotions {
    *
    * @return the weighted combination of the ground motions in this tree
    */
-  static GroundMotion combine(LogicTree<GroundMotion> tree) {
+  public static GroundMotion combine(LogicTree<GroundMotion> tree) {
     if (tree.size() == 1) {
       return tree.get(0).value();
     }