diff --git a/include/clang/Basic/Builtins.def b/include/clang/Basic/Builtins.def
index 5060e9e9e9..85504ac268 100644
--- a/include/clang/Basic/Builtins.def
+++ b/include/clang/Basic/Builtins.def
@@ -233,13 +233,12 @@ BUILTIN(__builtin_islessgreater , "i.", "nc")
 BUILTIN(__builtin_isunordered   , "i.", "nc")
 
 // Unary FP classification
-// BUILTIN(__builtin_fpclassify, "iiiii.", "nc")
+BUILTIN(__builtin_fpclassify, "iiiii.", "nc")
 BUILTIN(__builtin_isfinite,   "i.", "nc")
 BUILTIN(__builtin_isinf,      "i.", "nc")
 BUILTIN(__builtin_isinf_sign, "i.", "nc")
 BUILTIN(__builtin_isnan,      "i.", "nc")
 BUILTIN(__builtin_isnormal,   "i.", "nc")
-BUILTIN(__builtin_fpclassify, "iiiiii.", "nc")
 
 // Builtins for arithmetic.
 BUILTIN(__builtin_clz  , "iUi"  , "nc")
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 8db3eb1713..3c7492af61 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -4129,7 +4129,7 @@ private:
                                                     CallExpr *TheCall);
   bool SemaBuiltinVAStart(CallExpr *TheCall);
   bool SemaBuiltinUnorderedCompare(CallExpr *TheCall);
-  bool SemaBuiltinUnaryFP(CallExpr *TheCall);
+  bool SemaBuiltinFPClassification(CallExpr *TheCall, unsigned LastArg=1);
   bool SemaBuiltinStackAddress(CallExpr *TheCall);
 
 public:
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index 64cbde050b..f9466ca385 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -141,12 +141,16 @@ Sema::CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
     if (SemaBuiltinUnorderedCompare(TheCall))
       return ExprError();
     break;
+  case Builtin::BI__builtin_fpclassify:
+    if (SemaBuiltinFPClassification(TheCall, 6))
+      return ExprError();
+    break;
   case Builtin::BI__builtin_isfinite:
   case Builtin::BI__builtin_isinf:
   case Builtin::BI__builtin_isinf_sign:
   case Builtin::BI__builtin_isnan:
   case Builtin::BI__builtin_isnormal:
-    if (SemaBuiltinUnaryFP(TheCall))
+    if (SemaBuiltinFPClassification(TheCall))
       return ExprError();
     break;
   case Builtin::BI__builtin_return_address:
@@ -584,20 +588,21 @@ bool Sema::SemaBuiltinUnorderedCompare(CallExpr *TheCall) {
   return false;
 }
 
-/// SemaBuiltinUnorderedCompare - Handle functions like __builtin_isnan and
-/// friends.  This is declared to take (...), so we have to check everything.
-bool Sema::SemaBuiltinUnaryFP(CallExpr *TheCall) {
-  if (TheCall->getNumArgs() < 1)
+/// SemaBuiltinSemaBuiltinFPClassification - Handle functions like
+/// __builtin_isnan and friends.  This is declared to take (...), so we have
+/// to check everything.
+bool Sema::SemaBuiltinFPClassification(CallExpr *TheCall, unsigned LastArg) {
+  if (TheCall->getNumArgs() < LastArg)
     return Diag(TheCall->getLocEnd(), diag::err_typecheck_call_too_few_args)
       << 0 /*function call*/;
-  if (TheCall->getNumArgs() > 1)
-    return Diag(TheCall->getArg(1)->getLocStart(),
+  if (TheCall->getNumArgs() > LastArg)
+    return Diag(TheCall->getArg(LastArg)->getLocStart(),
                 diag::err_typecheck_call_too_many_args)
       << 0 /*function call*/
-      << SourceRange(TheCall->getArg(1)->getLocStart(),
+      << SourceRange(TheCall->getArg(LastArg)->getLocStart(),
                      (*(TheCall->arg_end()-1))->getLocEnd());
 
-  Expr *OrigArg = TheCall->getArg(0);
+  Expr *OrigArg = TheCall->getArg(LastArg-1);
 
   if (OrigArg->isTypeDependent())
     return false;
diff --git a/test/Sema/builtin-unary-fp.c b/test/Sema/builtin-unary-fp.c
index 8f48d7ffc5..57568db8ae 100644
--- a/test/Sema/builtin-unary-fp.c
+++ b/test/Sema/builtin-unary-fp.c
@@ -9,4 +9,8 @@ void a() {
   check(__builtin_isfinite(1)); // expected-error{{requires argument of floating point type}}
   check(__builtin_isinf()); // expected-error{{too few arguments}}
   check(__builtin_isnan(1,2)); // expected-error{{too many arguments}}
+  check(__builtin_fpclassify(0, 0, 0, 0, 0, 1.0));
+  check(__builtin_fpclassify(0, 0, 0, 0, 0, 1)); // expected-error{{requires argument of floating point type}}
+  check(__builtin_fpclassify(0, 0, 0, 0, 1)); // expected-error{{too few arguments}}
+  check(__builtin_fpclassify(0, 0, 0, 0, 0, 1, 0)); // expected-error{{too many arguments}}
 }