diff --git a/Phreeqc.h b/Phreeqc.h
index 01a49e457..5510379f7 100644
--- a/Phreeqc.h
+++ b/Phreeqc.h
@@ -6,7 +6,6 @@
 #      define WINVER 0x0400
 #    endif
 #    include <afx.h>
-// #    define nullptr NULL
 #  endif
 #  include <windows.h>
 #  if defined(PHREEQCI_GUI)
@@ -2096,7 +2095,7 @@ char* _string_duplicate(const char* token, const char* szFileName, int nLine);
 // https://stackoverflow.com/questions/2915672/snprintf-and-visual-studio-2010
 
 #if defined(_MSC_VER) && (_MSC_VER < 1900)
-#if (_MSC_VER == 1400) // VS2005
+#if (_MSC_VER <= 1700) // VS2012
 namespace std {
 	__inline bool isnan(double num) {
 		return _isnan(num) != 0;
diff --git a/global_structures.h b/global_structures.h
index 020770f77..c4672cfe0 100644
--- a/global_structures.h
+++ b/global_structures.h
@@ -6,7 +6,8 @@
  *   #define DEFINITIONS
  * ---------------------------------------------------------------------- */
 #if !defined(NAN)
-#  if defined(_MSC_VER) && (_MSC_VER <= 1400) // VS2005
+#  if defined(_MSC_VER) && (_MSC_VER <= 1700) // VS2012
+//   https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170     
 #    include <limits>
 #    define NAN std::numeric_limits<double>::signaling_NaN()
 #  else