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
@@ -99,6 +99,9 @@
       Diags->setClient(new IgnoringDiagConsumer);
     // Prepare to run a compiler.
     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);