diff --git a/include/llvm/CodeGen/CallingConvLower.h b/include/llvm/CodeGen/CallingConvLower.h
index f6a9f6c04d9..a953094b444 100644
--- a/include/llvm/CodeGen/CallingConvLower.h
+++ b/include/llvm/CodeGen/CallingConvLower.h
@@ -142,7 +142,10 @@ typedef bool CCCustomFn(unsigned &ValNo, MVT &ValVT,
                         MVT &LocVT, CCValAssign::LocInfo &LocInfo,
                         ISD::ArgFlagsTy &ArgFlags, CCState &State);
 
-typedef enum { Invalid, Prologue, Call } ParmContext;
+/// ParmContext - This enum tracks whether calling convention lowering is in
+/// the context of prologue or call generation. Not all backends make use of
+/// this information.
+typedef enum { Unknown, Prologue, Call } ParmContext;
 
 /// CCState - This class holds information needed while lowering arguments and
 /// return values.  It captures which registers are already assigned and which
diff --git a/lib/CodeGen/CallingConvLower.cpp b/lib/CodeGen/CallingConvLower.cpp
index eb90c049cd0..14eb0541dc8 100644
--- a/lib/CodeGen/CallingConvLower.cpp
+++ b/lib/CodeGen/CallingConvLower.cpp
@@ -28,7 +28,7 @@ CCState::CCState(CallingConv::ID CC, bool isVarArg, MachineFunction &mf,
                  LLVMContext &C)
   : CallingConv(CC), IsVarArg(isVarArg), MF(mf), TM(tm),
     TRI(*TM.getRegisterInfo()), Locs(locs), Context(C),
-    CallOrPrologue(Invalid) {
+    CallOrPrologue(Unknown) {
   // No stack is used.
   StackOffset = 0;