diff --git a/clang/unittests/Tooling/Syntax/TreeTest.cpp b/clang/unittests/Tooling/Syntax/TreeTest.cpp
--- a/clang/unittests/Tooling/Syntax/TreeTest.cpp
+++ b/clang/unittests/Tooling/Syntax/TreeTest.cpp
@@ -98,8 +98,12 @@
     if (!Diags->getClient())
       Diags->setClient(new IgnoringDiagConsumer);
     // Prepare to run a compiler.
-    std::vector<const char *> Args = {"syntax-test", "-std=c++11",
-                                      "-fsyntax-only", FileName};
+    std::vector<const char *> Args = {
+      "syntax-test", "-std=c++11",
+      // Hard-setting target so the unit test behavior doesn't depend on the
+      // host.
+      "-target", "x86_64-unknown-unknown",
+      "-fsyntax-only", FileName};
     Invocation = createInvocationFromCommandLine(Args, Diags, FS);
     assert(Invocation);
     Invocation->getFrontendOpts().DisableFree = false;