diff --git a/tests/compiler/type_decl/namespaced-composite-property-arginfo.phpt b/tests/compiler/type_decl/namespaced-composite-property-arginfo.phpt
new file mode 100644
index 00000000..7d034fff
--- /dev/null
+++ b/tests/compiler/type_decl/namespaced-composite-property-arginfo.phpt
@@ -0,0 +1,62 @@
+--TEST--
+Namespaced union and intersection properties generate valid arginfo identifiers
+--FILE--
+<?php
+
+namespace NamespacedArginfo {
+    interface Left
+    {
+    }
+
+    interface Right
+    {
+    }
+
+    final class Both implements Left, Right
+    {
+    }
+
+    final class Alternative
+    {
+    }
+
+    final class Holder
+    {
+        public Left|Alternative $union;
+        public Left&Right $intersection;
+
+        public function __construct(Left|Alternative $union, Left&Right $intersection)
+        {
+            $this->union = $union;
+            $this->intersection = $intersection;
+        }
+    }
+
+    function run(): void
+    {
+        $both = new Both();
+        $holder = new Holder(new Alternative(), $both);
+
+        echo (new \ReflectionProperty(Holder::class, 'union'))->getType(), "\n";
+        echo (new \ReflectionProperty(Holder::class, 'intersection'))->getType(), "\n";
+        var_dump($holder->union instanceof Alternative);
+        var_dump($holder->intersection instanceof Both);
+
+        $holder->union = $both;
+        var_dump($holder->union instanceof Both);
+    }
+}
+
+namespace {
+    function main(): void
+    {
+        \NamespacedArginfo\run();
+    }
+}
+?>
+--EXPECT--
+NamespacedArginfo\Left|NamespacedArginfo\Alternative
+NamespacedArginfo\Left&NamespacedArginfo\Right
+bool(true)
+bool(true)
+bool(true)