diff --git a/src/include/ngspice/cm.h b/src/include/ngspice/cm.h
index 42681f37e..d05cbf673 100644
--- a/src/include/ngspice/cm.h
+++ b/src/include/ngspice/cm.h
@@ -45,9 +45,11 @@ NON-STANDARD FEATURES
 #include "ngspice/cmproto.h"
 #include "ngspice/mifcmdat.h"
 
+#include <math.h>
+
 #if !defined(NAN)
-#if defined(_MSC_VER) && (_MSC_VER < 1800)
-    /* VS 2012 or less cannot evaluate 0.0/0.0 */
+#if defined(_MSC_VER)
+    /* NAN is not defined in VS 2012 or older */
     static const __int64 global_nan = 0x7ff8000000000000i64;
     #define NAN (*(const double *) &global_nan)
 #else
diff --git a/src/include/ngspice/ngspice.h b/src/include/ngspice/ngspice.h
index 2bd4fba73..086b214cf 100644
--- a/src/include/ngspice/ngspice.h
+++ b/src/include/ngspice/ngspice.h
@@ -206,8 +206,8 @@ extern double x_atanh(double);
 #endif
 
 #if !defined(NAN)
-#if defined(_MSC_VER) && (_MSC_VER < 1800)
-    /* VS 2012 or less cannot evaluate 0.0/0.0 */
+#if defined(_MSC_VER)
+    /* NAN is not defined in VS 2012 or older */
     static const __int64 global_nan = 0x7ff8000000000000i64;
     #define NAN (*(const double *) &global_nan)
 #else