diff --git a/src/include/ngspice/ngspice.h b/src/include/ngspice/ngspice.h
index 66060838d..05ebf2073 100644
--- a/src/include/ngspice/ngspice.h
+++ b/src/include/ngspice/ngspice.h
@@ -173,6 +173,7 @@
 #define strcasecmp _stricmp
 #define strncasecmp _strnicmp
 #define snprintf _snprintf
+#define isatty _isatty
 #define inline __inline
 /* NAN not available in MS VS 2008 */
 #ifndef NAN