diff --git a/sc2/src/port.h b/sc2/src/port.h
index 5f6522334..485e7b85d 100644
--- a/sc2/src/port.h
+++ b/sc2/src/port.h
@@ -142,6 +142,7 @@ typedef unsigned short mode_t;
 
 // String formatting
 #ifdef _MSC_VER
+#	include <stdarg.h>
 // Defined in port.c
 int snprintf(char *str, size_t size, const char *format, ...);
 int vsnprintf(char *str, size_t size, const char *format, va_list args);