diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 25aab58660cc2948b1fb9f7daba365f46928c8cb..ee86da6c340b5ee4b04399c263a1c576d749490d 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2281,6 +2281,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       A->render(Args, CmdArgs);
   }
 
+  // Don't warn about unused -flto.  This can happen when we're preprocessing or
+  // precompiling.
+  Args.ClaimAllArgs(options::OPT_flto);
+
   Args.AddAllArgs(CmdArgs, options::OPT_W_Group);
   if (Args.hasFlag(options::OPT_pedantic, options::OPT_no_pedantic, false))
     CmdArgs.push_back("-pedantic");