diff --git a/ext/reflection/php_reflection.c b/ext/reflection/php_reflection.c
index e74b7fcb27a7..860b4049a2fb 100644
--- a/ext/reflection/php_reflection.c
+++ b/ext/reflection/php_reflection.c
@@ -6763,8 +6763,7 @@ ZEND_METHOD(ReflectionProperty, isReadable)
 	}
 
 	if (prop->flags & ZEND_ACC_VIRTUAL) {
-		ZEND_ASSERT(prop->hooks);
-		if (!prop->hooks[ZEND_PROPERTY_HOOK_GET]) {
+		if (prop->hooks && !prop->hooks[ZEND_PROPERTY_HOOK_GET]) {
 			RETURN_FALSE;
 		}
 	} else if (obj && (!prop->hooks || !prop->hooks[ZEND_PROPERTY_HOOK_GET])) {
@@ -6855,8 +6854,7 @@ ZEND_METHOD(ReflectionProperty, isWritable)
 	}
 
 	if (prop->flags & ZEND_ACC_VIRTUAL) {
-		ZEND_ASSERT(prop->hooks);
-		if (!prop->hooks[ZEND_PROPERTY_HOOK_SET]) {
+		if (prop->hooks && !prop->hooks[ZEND_PROPERTY_HOOK_SET]) {
 			RETURN_FALSE;
 		}
 	} else if (obj && (prop->flags & ZEND_ACC_READONLY)) {
diff --git a/ext/reflection/tests/gh21768.phpt b/ext/reflection/tests/gh21768.phpt
new file mode 100644
index 000000000000..422239120dbe
--- /dev/null
+++ b/ext/reflection/tests/gh21768.phpt
@@ -0,0 +1,21 @@
+--TEST--
+GH-21768: Assertion failure in ReflectionProperty::is{Readable,Writable}() on internal virtual properties
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$rc = new ReflectionClass('DOMDocument');
+foreach ($rc->getProperties() as $rp) {
+    if (!$rp->isVirtual())
+	    continue;
+    if (!$rp->isReadable(null))
+	    die("$rp should be readable");
+    if (!$rp->isWritable(null))
+	    die("$rp should be writable");
+}
+echo "done\n";
+
+?>
+--EXPECT--
+done