diff --git a/lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp b/lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp
index ab5dab5839b..941160ca5f8 100644
--- a/lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp
+++ b/lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp
@@ -19,7 +19,7 @@
 #include <map>
 #include <dlfcn.h>
 #include <link.h>
-#include <math.h>
+#include <cmath>
 #include <stdio.h>
 using std::vector;
 
@@ -217,14 +217,6 @@ GenericValue lle_X_log(FunctionType *M, const vector<GenericValue> &Args) {
   return GV;
 }
 
-// int isnan(double value);
-GenericValue lle_X_isnan(FunctionType *F, const vector<GenericValue> &Args) {
-  assert(Args.size() == 1);
-  GenericValue GV;
-  GV.IntVal = std::isnan(Args[0].DoubleVal);
-  return GV;
-}
-
 // double floor(double)
 GenericValue lle_X_floor(FunctionType *M, const vector<GenericValue> &Args) {
   assert(Args.size() == 1);
@@ -744,7 +736,6 @@ void Interpreter::initializeExternalFunctions() {
   FuncNames["lle_X_pow"]          = lle_X_pow;
   FuncNames["lle_X_exp"]          = lle_X_exp;
   FuncNames["lle_X_log"]          = lle_X_log;
-  FuncNames["lle_X_isnan"]        = lle_X_isnan;
   FuncNames["lle_X_floor"]        = lle_X_floor;
   FuncNames["lle_X_srand"]        = lle_X_srand;
   FuncNames["lle_X_drand48"]      = lle_X_drand48;