diff --git a/src/IntervalTree.php b/src/IntervalTree.php
index 08c2704..d2aafce 100644
--- a/src/IntervalTree.php
+++ b/src/IntervalTree.php
@@ -290,7 +290,7 @@ private function deleteFixup(Node $fixNode): void
                     $brotherNode = $currentNode->getParent()->getRight();
                 }
 
-                if ($brotherNode->getLeft()->getColor()->isBlack()) {
+                if ($brotherNode->getLeft()->getColor()->isBlack() && $brotherNode->getRight()->getColor()->isBlack()) {
                     $brotherNode->setColor(NodeColor::red());
                     $currentNode = $currentNode->getParent();
                 } else {
@@ -298,6 +298,7 @@ private function deleteFixup(Node $fixNode): void
                         $brotherNode->setColor(NodeColor::red());
                         $brotherNode->getLeft()->setColor(NodeColor::black());
                         $this->rotateRight($brotherNode);
+                        $brotherNode = $currentNode->getParent()->getRight();
                     }
                     $brotherNode->setColor($currentNode->getParent()->getColor());
                     $currentNode->getParent()->setColor(NodeColor::black());
@@ -313,7 +314,7 @@ private function deleteFixup(Node $fixNode): void
                     $this->rotateRight($currentNode->getParent());
                     $brotherNode = $currentNode->getParent()->getLeft();
                 }
-                if ($brotherNode->getRight()->getColor()->isBlack()) {
+                if ($brotherNode->getRight()->getColor()->isBlack() && $brotherNode->getLeft()->getColor()->isBlack()) {
                     $brotherNode->setColor(NodeColor::red());
                     $currentNode = $currentNode->getParent();
                 } else {
@@ -321,6 +322,7 @@ private function deleteFixup(Node $fixNode): void
                         $brotherNode->setColor(NodeColor::red());
                         $brotherNode->getRight()->setColor(NodeColor::black());
                         $this->rotateLeft($brotherNode);
+                        $brotherNode = $currentNode->getParent()->getLeft();
                     }
                     $brotherNode->setColor($currentNode->getParent()->getColor());
                     $currentNode->getParent()->setColor(NodeColor::black());
@@ -473,7 +475,7 @@ private function rotateRight(Node $y): void
 
         $x = $y->getParent();
         if ($x !== null && $x !== $this->nilNode) {
-            $y->updateMax();
+            $x->updateMax();
         }
     }
 
diff --git a/tests/IntervalTreeRandomizedTest.php b/tests/IntervalTreeRandomizedTest.php
new file mode 100644
index 0000000..e573ca3
--- /dev/null
+++ b/tests/IntervalTreeRandomizedTest.php
@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Danon\IntervalTree\Tests;
+
+use Danon\IntervalTree\Interval\NumericInterval;
+use Danon\IntervalTree\IntervalTree;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Compares the tree against a brute-force list under a random mix of
+ * inserts and removals.  Intervals are kept distinct so that the test
+ * exercises rebalancing and max-augmentation rather than duplicate handling.
+ *
+ * @covers \Danon\IntervalTree\IntervalTree
+ * @uses \Danon\IntervalTree\Interval\NumericInterval
+ * @uses \Danon\IntervalTree\Node
+ * @uses \Danon\IntervalTree\NodeColor
+ * @uses \Danon\IntervalTree\Pair
+ */
+final class IntervalTreeRandomizedTest extends TestCase
+{
+    /**
+     * @return array<string, array{int}>
+     */
+    public function provideSeeds(): array
+    {
+        $seeds = [];
+        for ($seed = 1; $seed <= 50; $seed++) {
+            $seeds["seed $seed"] = [$seed];
+        }
+        return $seeds;
+    }
+
+    /**
+     * @dataProvider provideSeeds
+     */
+    public function testRandomInsertRemoveMatchesBruteForce(int $seed): void
+    {
+        mt_srand($seed);
+        /** @var IntervalTree<int, int> $tree */
+        $tree = new IntervalTree();
+        /** @var array<int, array{int, int}> $live */
+        $live = [];
+        for ($op = 1; $op <= 300; $op++) {
+            if (count($live) < 2 || mt_rand(0, 2) > 0) {
+                $low = mt_rand(0, 1000) * 1000 + $op;
+                $high = $low + mt_rand(0, 30000);
+                $tree->insert(new NumericInterval($low, $high), $op);
+                $live[$op] = [$low, $high];
+            } else {
+                $value = array_rand($live);
+                [$low, $high] = $live[$value];
+                self::assertTrue($tree->remove(new NumericInterval($low, $high), $value));
+                unset($live[$value]);
+            }
+
+            $queryLow = mt_rand(0, 1030000);
+            $queryHigh = $queryLow + mt_rand(0, 20000);
+            $expected = [];
+            foreach ($live as $value => [$low, $high]) {
+                if (!($high < $queryLow || $queryHigh < $low)) {
+                    $expected[] = $value;
+                }
+            }
+            $actual = [];
+            foreach ($tree->findIntersections(new NumericInterval($queryLow, $queryHigh)) as $pair) {
+                $actual[] = $pair->getValue();
+            }
+            sort($expected);
+            sort($actual);
+            self::assertSame($expected, $actual, "seed $seed, operation $op");
+            self::assertSame(count($live), $tree->getSize());
+        }
+    }
+}