Index: include/clang/Driver/CLCompatOptions.td
===================================================================
--- include/clang/Driver/CLCompatOptions.td
+++ include/clang/Driver/CLCompatOptions.td
@@ -122,6 +122,8 @@
   Alias<show_includes>;
 def _SLASH_source_charset : CLCompileJoined<"source-charset:">,
   HelpText<"Source encoding, supports only UTF-8">, Alias<finput_charset_EQ>;
+def _SLASH_execution_charset : CLCompileJoined<"execution-charset:">,
+  HelpText<"Runtime encoding, supports only UTF-8">, Alias<fexec_charset_EQ>;
 def _SLASH_std : CLCompileJoined<"std:">,
   HelpText<"Language standard to compile for">;
 def _SLASH_U : CLJoinedOrSeparate<"U">, HelpText<"Undefine macro">,
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -5843,7 +5843,7 @@
   // -fexec_charset=UTF-8 is default. Reject others
   if (Arg *execCharset = Args.getLastArg(options::OPT_fexec_charset_EQ)) {
     StringRef value = execCharset->getValue();
-    if (value != "UTF-8")
+    if (value.lower() != "utf-8")
       D.Diag(diag::err_drv_invalid_value) << execCharset->getAsString(Args)
                                           << value;
   }
Index: test/Driver/cl-options.c
===================================================================
--- test/Driver/cl-options.c
+++ test/Driver/cl-options.c
@@ -184,6 +184,10 @@
 // RUN: %clang_cl /source-charset:utf-16 -### -- %s 2>&1 | FileCheck -check-prefix=source-charset-utf-16 %s
 // source-charset-utf-16: invalid value 'utf-16'
 
+// /execution-charset: should warn on everything except UTF-8.
+// RUN: %clang_cl /execution-charset:utf-16 -### -- %s 2>&1 | FileCheck -check-prefix=execution-charset-utf-16 %s
+// execution-charset-utf-16: invalid value 'utf-16'
+//
 // RUN: %clang_cl /Umymacro -### -- %s 2>&1 | FileCheck -check-prefix=U %s
 // RUN: %clang_cl /U mymacro -### -- %s 2>&1 | FileCheck -check-prefix=U %s
 // U: "-U" "mymacro"
@@ -289,6 +293,7 @@
 // RUN:    /d2FastFail \
 // RUN:    /d2Zi+ \
 // RUN:    /errorReport:foo \
+// RUN:    /execution-charset:utf-8 \
 // RUN:    /FC \
 // RUN:    /Fdfoo \
 // RUN:    /FS \