diff --git a/src/lib_json/json_writer.cpp b/src/lib_json/json_writer.cpp
index 3b22ee8..b8c7223 100644
--- a/src/lib_json/json_writer.cpp
+++ b/src/lib_json/json_writer.cpp
@@ -68,6 +68,25 @@
 #define snprintf _snprintf
 #endif
 
+#if defined(_MSC_VER) && !defined(__clang__)
+#if _MSC_VER >= 1900 && defined(_WIN64)
+#include <math.h>
+#define isnan _isnanf
+#else
+#include <float.h>
+#define isnan _isnan
+#endif
+#elif __cplusplus >= 201103L
+#include <cmath>
+#define isnan std::isnan
+#else
+#include <math.h>
+#if !define(isnan)
+// IEEE standard states that NaN values will not compare to themselves
+#define isnan(x) (x!=x)
+#endif
+#endif
+
 #if defined(_MSC_VER) && _MSC_VER >= 1400 // VC++ 8.0
 // Disable warning about strdup being deprecated.
 #pragma warning(disable : 4996)
@@ -148,7 +167,7 @@ JSONCPP_STRING valueToString(double value, bool useSpecialFloats, unsigned int p
     }
 
   } else {
-    // IEEE standard states that NaN values will not compare to themselves
+
     if (isnan(value)) {
       len = snprintf(buffer, sizeof(buffer), useSpecialFloats ? "NaN" : "null");
     } else if (value < 0) {
diff --git a/src/test_lib_json/main.cpp b/src/test_lib_json/main.cpp
index 9cddf41..a0c26eb 100644
--- a/src/test_lib_json/main.cpp
+++ b/src/test_lib_json/main.cpp
@@ -18,6 +18,7 @@
 #include <sstream>
 #include <string>
 #include <iomanip>
+#include <cmath>
 
 // Make numeric limits more convenient to talk about.
 // Assumes int type in 32 bits.
@@ -2405,7 +2406,7 @@ JSONTEST_FIXTURE(CharReaderAllowSpecialFloatsTest, issue209) {
     JSONTEST_ASSERT_STRING_EQUAL("", errs);
     JSONTEST_ASSERT_EQUAL(3u, root.size());
     double n = root["a"].asDouble();
-    JSONTEST_ASSERT(isnan(n));
+    JSONTEST_ASSERT(std::isnan(n));
     JSONTEST_ASSERT_EQUAL(std::numeric_limits<double>::infinity(), root.get("b", 0.0));
     JSONTEST_ASSERT_EQUAL(-std::numeric_limits<double>::infinity(), root.get("c", 0.0));
   }