diff --git a/framework/Collections/TPriorityMap.php b/framework/Collections/TPriorityMap.php
index 8e8c824dc..9ec3fea9a 100644
--- a/framework/Collections/TPriorityMap.php
+++ b/framework/Collections/TPriorityMap.php
@@ -98,6 +98,15 @@ private function getPriorityCombineStyle(): bool
 		return false;
 	}
 
+	/**
+	 * @return int This is the key for the next appended item that doesn't have its
+	 *   own key.
+	 */
+	public function getNextIntegerKey(): int
+	{
+		return $this->_ic;
+	}
+
 	/**
 	 * @return int the number of items in the map
 	 */
diff --git a/tests/unit/Collections/TPriorityMapTest.php b/tests/unit/Collections/TPriorityMapTest.php
index 9dec2608f..ae9a27c95 100644
--- a/tests/unit/Collections/TPriorityMapTest.php
+++ b/tests/unit/Collections/TPriorityMapTest.php
@@ -288,15 +288,24 @@ public function testArrayReadTPriorityMap()
 	
 	public function testArrayWriteTPriorityMap()
 	{
+		$this->assertEquals(0, $this->map->getNextIntegerKey());
 		$this->map[] = $this->item1;
+		$this->assertEquals(1, $this->map->getNextIntegerKey());
 		$this->map->add(null, $this->item2, 15);
+		$this->assertEquals(2, $this->map->getNextIntegerKey());
 		$this->map[] = $this->item3;
+		$this->assertEquals(3, $this->map->getNextIntegerKey());
 		$this->map->add(null, $this->item4, 5);
+		$this->assertEquals(4, $this->map->getNextIntegerKey());
 		$this->assertEquals($this->item1, $this->map[0]);
 		$this->assertEquals($this->item2, $this->map[1]);
 		$this->assertEquals($this->item3, $this->map[2]);
 		$this->assertEquals($this->item4, $this->map[3]);
 		$this->assertNull($this->map[4]);
+		
+		$this->map[11] = $this->item1;
+		$this->assertEquals($this->item1, $this->map[11]);
+		$this->assertEquals(12, $this->map->getNextIntegerKey());
 	}
 	
 	// **    End TMap tests on TPriorityMap