diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -6152,7 +6152,8 @@
 def _SLASH_W2 : CLFlag<"W2">, HelpText<"Enable -Wall">, Alias<Wall>;
 def _SLASH_W3 : CLFlag<"W3">, HelpText<"Enable -Wall">, Alias<Wall>;
 def _SLASH_W4 : CLFlag<"W4">, HelpText<"Enable -Wall and -Wextra">, Alias<WCL4>;
-def _SLASH_Wall : CLFlag<"Wall">, HelpText<"Enable -Weverything">,
+def _SLASH_Wall : Option<["/"], "Wall", KIND_FLAG>, Group<cl_Group>,
+  Flags<[CLOption, NoXarchOption]>, HelpText<"Enable -Weverything">,
   Alias<W_Joined>, AliasArgs<["everything"]>;
 def _SLASH_WX : CLFlag<"WX">, HelpText<"Treat warnings as errors">,
   Alias<W_Joined>, AliasArgs<["error"]>;
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -266,9 +266,11 @@
 // RUN: %clang_cl /W3 -### -- %s 2>&1 | FileCheck -check-prefix=W1 %s
 // RUN: %clang_cl /W4 -### -- %s 2>&1 | FileCheck -check-prefix=W4 %s
 // RUN: %clang_cl /Wall -### -- %s 2>&1 | FileCheck -check-prefix=Weverything %s
+// RUN: %clang_cl -Wall -### -- %s 2>&1 | FileCheck -check-prefix=Wall %s
 // W1: -Wall
 // W4: -WCL4
 // Weverything: -Weverything
+// Wall: -Wall
 
 // RUN: %clang_cl /WX -### -- %s 2>&1 | FileCheck -check-prefix=WX %s
 // WX: -Werror