diff --git a/clang/lib/Driver/ToolChains/Arch/X86.cpp b/clang/lib/Driver/ToolChains/Arch/X86.cpp
--- a/clang/lib/Driver/ToolChains/Arch/X86.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/X86.cpp
@@ -119,6 +119,15 @@
 void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
                                const ArgList &Args,
                                std::vector<StringRef> &Features) {
+  // Claim and report unsupported -mabi=. Note: we don't support "sysv_abi" or
+  // "ms_abi" as default function attributes.
+  if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_mabi_EQ)) {
+    StringRef DefaultAbi = Triple.isOSWindows() ? "ms" : "sysv";
+    if (A->getValue() != DefaultAbi)
+      D.Diag(diag::err_drv_unsupported_opt_for_target)
+          << A->getSpelling() << Triple.getTriple();
+  }
+
   // If -march=native, autodetect the feature list.
   if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_march_EQ)) {
     if (StringRef(A->getValue()) == "native") {
diff --git a/clang/test/Driver/mabi.c b/clang/test/Driver/mabi.c
deleted file mode 100644
--- a/clang/test/Driver/mabi.c
+++ /dev/null
@@ -1,6 +0,0 @@
-// RUN: %clang --target=i386-unknown-linux -mabi=ms -S %s -### 2>&1 | FileCheck --check-prefix=CHECK %s
-
-int f() {
-  // CHECK: warning: argument unused during compilation: '-mabi=ms'
-  return 0;
-}
diff --git a/clang/test/Driver/x86-mabi.c b/clang/test/Driver/x86-mabi.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/x86-mabi.c
@@ -0,0 +1,13 @@
+// RUN: %clang -### --target=x86_64-windows-msvc -mabi=ms -S %s 2>&1 | FileCheck %s
+// RUN: %clang -### --target=i386-unknown-linux -mabi=ms -S %s 2>&1 | FileCheck --check-prefix=ERR %s
+// RUN: %clang -### --target=x86_64-windows-msvc -mabi=sysv -S %s 2>&1 | FileCheck --check-prefix=ERR %s
+// RUN: %clang -### --target=i386-unknown-linux -mabi=sysv -S %s 2>&1 | FileCheck %s
+
+// RUN: %clang -### --target=x86_64-windows-gnu -mabi=ms -S %s 2>&1 | FileCheck %s
+
+// CHECK-NOT: {{error|warning}}:
+// ERR: error: unsupported option '-mabi=' for target '{{.*}}'
+
+int f() {
+  return 0;
+}