Index: clang/test/CXX/drs/dr13xx.cpp
===================================================================
--- clang/test/CXX/drs/dr13xx.cpp
+++ clang/test/CXX/drs/dr13xx.cpp
@@ -3,6 +3,16 @@
 // RUN: %clang_cc1 -std=c++14 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++17 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 
+#if __cplusplus >= 201103L
+namespace dr1305 { // dr1305: yes
+  struct Incomplete; // expected-note {{forward declaration of 'dr1305::Incomplete'}}
+  struct Complete {};
+
+  int incomplete = alignof(Incomplete(&)[]); // expected-error {{invalid application of 'alignof' to an incomplete type 'dr1305::Incomplete'}}
+  int complete = alignof(Complete(&)[]);
+}
+#endif
+
 __extension__ typedef __SIZE_TYPE__ size_t;
 
 namespace std {
Index: clang/www/cxx_dr_status.html
===================================================================
--- clang/www/cxx_dr_status.html
+++ clang/www/cxx_dr_status.html
@@ -7644,7 +7644,7 @@
     <td><a href="https://wg21.link/cwg1305">1305</a></td>
     <td>CD3</td>
     <td><TT>alignof</TT> applied to array of unknown size</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="full" align="center">Yes</td>
   </tr>
   <tr id="1306">
     <td><a href="https://wg21.link/cwg1306">1306</a></td>