Index: cfe/trunk/include/clang/Driver/CLCompatOptions.td
===================================================================
--- cfe/trunk/include/clang/Driver/CLCompatOptions.td
+++ cfe/trunk/include/clang/Driver/CLCompatOptions.td
@@ -394,7 +394,7 @@
 
 // Unsupported:
 
-def _SLASH_AI : CLJoined<"AI">;
+def _SLASH_AI : CLJoinedOrSeparate<"AI">;
 def _SLASH_Bt : CLFlag<"Bt">;
 def _SLASH_Bt_plus : CLFlag<"Bt+">;
 def _SLASH_clr : CLJoined<"clr">;
Index: cfe/trunk/test/Driver/cl-options.c
===================================================================
--- cfe/trunk/test/Driver/cl-options.c
+++ cfe/trunk/test/Driver/cl-options.c
@@ -387,6 +387,7 @@
 // (/Zs is for syntax-only)
 // RUN: %clang_cl /Zs \
 // RUN:     /AIfoo \
+// RUN:     /AI foo_does_not_exist \
 // RUN:     /Bt \
 // RUN:     /Bt+ \
 // RUN:     /clr:pure \