diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 04463be..808c31c 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -955,9 +955,14 @@
   if (Args.hasFlag(options::OPT_fdiagnostics_show_option,
                    options::OPT_fno_diagnostics_show_option))
     CmdArgs.push_back("-fdiagnostics-show-option");
-  if (!Args.hasFlag(options::OPT_fcolor_diagnostics,
-                    options::OPT_fno_color_diagnostics))
-    CmdArgs.push_back("-fno-color-diagnostics");
+
+  // Color diagnostics are the default, unless the terminal doesn't support
+  // them.
+  if (Args.hasFlag(options::OPT_fcolor_diagnostics,
+                   options::OPT_fno_color_diagnostics) &&
+      llvm::sys::Process::StandardErrHasColors())
+    CmdArgs.push_back("-fcolor-diagnostics");
+
   if (!Args.hasFlag(options::OPT_fshow_source_location,
                     options::OPT_fno_show_source_location))
     CmdArgs.push_back("-fno-show-source-location");