diff --git a/examples/javascript/working/521/Base.js b/examples/javascript/working/521/Base.js
new file mode 100644
index 0000000..18a55d0
--- /dev/null
+++ b/examples/javascript/working/521/Base.js
@@ -0,0 +1,4 @@
+module.exports = {
+  'to be [FAILED]' : function(test) {},
+  'to be [FAILED]' : function() {}
+}
diff --git a/examples/javascript/working/521/Expected.js b/examples/javascript/working/521/Expected.js
new file mode 100644
index 0000000..dd5a772
--- /dev/null
+++ b/examples/javascript/working/521/Expected.js
@@ -0,0 +1,8 @@
+module.exports = {
+  'to be [FAILED]' : function(test) {},
+  'to be [FAILED]' : function() {},
+  'to be with message [PASSED]' : function(test) {
+    var expect = this.client.api.expect.element('#weblogin').to.be.an('input', 'weblogin should be an input');
+    this.client.on('nightwatch:finished', function(results, errors) {})
+  },
+}
diff --git a/examples/javascript/working/521/Left.js b/examples/javascript/working/521/Left.js
new file mode 100644
index 0000000..ffb705e
--- /dev/null
+++ b/examples/javascript/working/521/Left.js
@@ -0,0 +1,8 @@
+module.exports = {
+  'to be [FAILED]' : function(test) {},
+  'to be [FAILED]' : function() {},
+  'to be with message [PASSED]' : function(test) {
+    var expect = this.client.api.expect.element('#weblogin').to.be.an('input', 'weblogin should be an input');
+    this.client.on('nightwatch:finished', function(results, errors) {})
+  }
+}
diff --git a/examples/javascript/working/521/Right.js b/examples/javascript/working/521/Right.js
new file mode 100644
index 0000000..2d54a16
--- /dev/null
+++ b/examples/javascript/working/521/Right.js
@@ -0,0 +1,4 @@
+module.exports = {
+  'to be [FAILED]' : function(test) {},
+  'to be [FAILED]' : function() {},
+}
diff --git a/src/merged_tree/postprocess.rs b/src/merged_tree/postprocess.rs
index ea4e7b4..66b1211 100644
--- a/src/merged_tree/postprocess.rs
+++ b/src/merged_tree/postprocess.rs
@@ -6,7 +6,7 @@ use regex::Regex;
 
 use crate::{
     ast::AstNode,
-    class_mapping::{ClassMapping, Leader, RevNode, RevisionNESet},
+    class_mapping::{ClassMapping, Leader, RevNode},
     lang_profile::CommutativeParent,
     merged_tree::MergedTree,
     pcs::Revision,
@@ -270,11 +270,8 @@ fn merge_same_sigs<'a>(
         let v = add_separators(left_revnodes, separator, add_separator)
             .into_iter()
             .map(|rev_node| {
-                MergedTree::new_exact(
-                    class_mapping.map_to_leader(rev_node),
-                    RevisionNESet::singleton(Revision::Left).with(Revision::Right),
-                    class_mapping,
-                )
+                let leader = class_mapping.map_to_leader(rev_node);
+                MergedTree::new_exact(leader, class_mapping.revision_set(&leader), class_mapping)
             })
             .collect();
         (v, false)