diff --git a/avl.js b/avl.js
index eb78565..31f67da 100644
--- a/avl.js
+++ b/avl.js
@@ -153,12 +153,10 @@ class AVLTree extends RankedTree {
                 this.record("Updating rank of nodes affected by rotations", n);
             });
 
-        return factor == 0;
+        return factor != 0;
     }
 
-    deleteFixup(y, parent) {
-        let x = y ? y : parent;
-
+    deleteFixup(x, parent) {
         let factor = balanceFactor(x);
         switch (factor) {
             case 0:
@@ -168,10 +166,10 @@ class AVLTree extends RankedTree {
                     x
                 );
 
-                return false;
+                return true;
             case -1:
             case 1:
-                return true;
+                return false;
         }
 
         let rotatingAroundRoot = x.parent == null;
@@ -201,8 +199,15 @@ class AVLTree extends RankedTree {
     }
 
     deleteRebalance(node, parent) {
-        while (node || parent) {
-            this.deleteFixup(node, parent);
+        if (!node && !parent) {
+            return;
+        }
+
+        if (!node) {
+            [node, parent] = [parent, parent.parent];
+        }
+
+        while (node && this.deleteFixup(node, parent)) {
             [node, parent] = [parent, parent ? parent.parent : null];
         }
     }