diff --git a/src/Psalm/Type/Reconciler.php b/src/Psalm/Type/Reconciler.php
index aab2847ebd1..c354b4e05a4 100644
--- a/src/Psalm/Type/Reconciler.php
+++ b/src/Psalm/Type/Reconciler.php
@@ -552,7 +552,9 @@ private static function getValueForKey(
                             return Type::getMixed($inside_loop);
                         } elseif ($existing_key_type_part instanceof TString) {
                             $new_base_type_candidate = Type::getString();
-                        } elseif ($existing_key_type_part instanceof Type\Atomic\TNamedObject) {
+                        } elseif ($existing_key_type_part instanceof Type\Atomic\TNamedObject
+                            && ($has_isset || $has_inverted_isset)
+                        ) {
                             $has_object_array_access = true;
                             return null;
                         } elseif (!$existing_key_type_part instanceof Type\Atomic\ObjectLike) {
diff --git a/tests/ArrayAccessTest.php b/tests/ArrayAccessTest.php
index 9dcbb9bc669..1511bea8087 100644
--- a/tests/ArrayAccessTest.php
+++ b/tests/ArrayAccessTest.php
@@ -906,6 +906,69 @@ function foo(SimpleXMLElement $s) : SimpleXMLElement {
                         return $s["a"];
                     }',
             ],
+            'assertOnArrayAccess' => [
+                '<?php
+                    class A {
+                        public function foo() : void {}
+                    }
+
+                    class C implements ArrayAccess
+                    {
+                        /**
+                         * @var array
+                         */
+                        protected $data = [];
+
+                        /**
+                         * @param string $name
+                         * @return mixed
+                         */
+                        public function offsetGet($name)
+                        {
+                            return $this->data[$name];
+                        }
+
+                        /**
+                         * @param string $name
+                         * @param mixed $value
+                         */
+                        public function offsetSet($name, $value) : void
+                        {
+                            $this->data[$name] = $value;
+                        }
+
+                        public function __isset(string $name) : bool
+                        {
+                            return isset($this->data[$name]);
+                        }
+
+                        public function __unset(string $name) : void
+                        {
+                            unset($this->data[$name]);
+                        }
+
+                        /**
+                         * @psalm-suppress MixedArgument
+                         */
+                        public function offsetExists($offset) : bool
+                        {
+                            return $this->__isset($offset);
+                        }
+
+                        /**
+                         * @psalm-suppress MixedArgument
+                         */
+                        public function offsetUnset($offset) : void
+                        {
+                            $this->__unset($offset);
+                        }
+                    }
+
+                    $container = new C();
+                    if ($container["a"] instanceof A) {
+                        $container["a"]->foo();
+                    }'
+            ],
         ];
     }