diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 719a631a7..2d8caa2 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -814,6 +814,10 @@
   DefineFloatMacros(Builder, "FLT", &TI.getFloatFormat(), "F");
   DefineFloatMacros(Builder, "DBL", &TI.getDoubleFormat(), "");
   DefineFloatMacros(Builder, "LDBL", &TI.getLongDoubleFormat(), "L");
+  if (TI.hasFloat128Type())
+    // FIXME: Switch away from the non-standard "Q" when we can
+    DefineFloatMacros(Builder, "FLT128", &TI.getFloat128Format(), "Q");
+
 
   // Define a __POINTER_WIDTH__ macro for stdint.h.
   Builder.defineMacro("__POINTER_WIDTH__",