diff --git a/sample_files/change_outer_after.el b/sample_files/change_outer_after.el
new file mode 100644
index 000000000..0d17e3002
--- /dev/null
+++ b/sample_files/change_outer_after.el
@@ -0,0 +1 @@
+[(lhs) comma rhs]
diff --git a/sample_files/change_outer_before.el b/sample_files/change_outer_before.el
new file mode 100644
index 000000000..63b007fc4
--- /dev/null
+++ b/sample_files/change_outer_before.el
@@ -0,0 +1 @@
+(lhs comma rhs)
diff --git a/sample_files/compare.expected b/sample_files/compare.expected
index 0a00bc03d..4f9d39849 100644
--- a/sample_files/compare.expected
+++ b/sample_files/compare.expected
@@ -1,6 +1,9 @@
 sample_files/bad_combine_before.rs sample_files/bad_combine_after.rs
 ffb31b7f11712d0e28a7f874bb7756c6  -
 
+sample_files/change_outer_before.el sample_files/change_outer_after.el
+1e144818ad54091b05e58e2c617add8f  -
+
 sample_files/clojure_before.clj sample_files/clojure_after.clj
 8316bcd959ce706ac07011f6dc31c93a  -
 
@@ -77,10 +80,10 @@ sample_files/simple_before.txt sample_files/simple_after.txt
 4b653ebe89321835c35722dd065cf6a2  -
 
 sample_files/slider_before.rs sample_files/slider_after.rs
-9b21c5790773eaba1a83e92fe2b9b5a8  -
+ab11d8dfc684921d85f49d3ec4dfeec4  -
 
 sample_files/slow_before.rs sample_files/slow_after.rs
-07c6dda6ca91de93a0553f90060697d0  -
+1f6176a6518e16eb8dfe32d7d81c63d9  -
 
 sample_files/small_before.js sample_files/small_after.js
 ee97a525a74be6dd18e959395d02265b  -
diff --git a/src/graph.rs b/src/graph.rs
index aa412b689..b0ea71c3c 100644
--- a/src/graph.rs
+++ b/src/graph.rs
@@ -71,6 +71,11 @@ impl<'a> PartialEq for Vertex<'a> {
             // the graph size relative to tree depth.
             && self.lhs_parent_id == other.lhs_parent_id
             && self.rhs_parent_id == other.rhs_parent_id
+            // We do want to distinguish whether we can pop each side
+            // independently though. Without this, if we find a case
+            // where we can pop sides together, we don't consider the
+            // case where we get a better diff by popping each side
+            // separately.
             && self.can_pop_either == other.can_pop_either
     }
 }