diff --git a/src/mol-model/structure/structure/structure.ts b/src/mol-model/structure/structure/structure.ts
index 46abc6d3b7d90e4b719779330c187089e02890ed..e42d697cc127f7832100787a02b96c101453fd28 100644
--- a/src/mol-model/structure/structure/structure.ts
+++ b/src/mol-model/structure/structure/structure.ts
@@ -1059,6 +1059,7 @@ namespace Structure {
     }
 
     export function areUnitIdsAndIndicesEqual(a: Structure, b: Structure) {
+        if (a === b) return true;
         if (!areUnitIdsEqual(a, b)) return false;
 
         for (let i = 0, il = a.units.length; i < il; i++) {
diff --git a/src/mol-model/structure/structure/unit.ts b/src/mol-model/structure/structure/unit.ts
index fe2c5b7b8c9bdde0f498fcfb4e9a6f785eb72a5f..8d64234ad3e1d4a888e337233630a5562bfa00c9 100644
--- a/src/mol-model/structure/structure/unit.ts
+++ b/src/mol-model/structure/structure/unit.ts
@@ -490,6 +490,7 @@ namespace Unit {
     }
 
     export function areConformationsEqual(a: Unit, b: Unit) {
+        if (a === b) return true;
         if (!SortedArray.areEqual(a.elements, b.elements)) return false;
         return isSameConformation(a, b.model);
     }