diff --git a/plugins/ets/tests/ets_test_suite/gc/stress/test_gc_old.ets b/plugins/ets/tests/ets_test_suite/gc/stress/test_gc_old.ets
index c473fac81a8662a344ceb58040b4f43797fbed93..a0b717f3be8bc8d41afd3f08fcbac17b3e4ccf18 100644
--- a/plugins/ets/tests/ets_test_suite/gc/stress/test_gc_old.ets
+++ b/plugins/ets/tests/ets_test_suite/gc/stress/test_gc_old.ets
@@ -50,7 +50,7 @@ class TestGCOld {
     private static mutatorSum : long = 0;
     private static aexport : int[];
 
-    private static trees : TreeNode[] | null;
+    private static trees : (TreeNode | null)[] | null;
     private static where : int = 0;
     private static rnd = new Random();
 
@@ -175,7 +175,7 @@ class TestGCOld {
             }
             path >>= 1;
         }
-        let tmp : TreeNode;
+        let tmp : TreeNode | null;
         if ((path & 1) == 0) {
             tmp = tn1.left;
             tn1.left = tn2.left;
@@ -208,7 +208,7 @@ class TestGCOld {
                     }
     }
 
-    private static replaceTree(full : TreeNode, partial : TreeNode) : void {
+    private static replaceTree(full : TreeNode | null, partial : TreeNode | null) : void {
         let dir : boolean = (partial.value % 2) == 0;
         TestGCOld.actuallyMut++;
         TestGCOld.doReplaceTreeWork(full, partial, dir);