diff --git a/n.h b/n.h
index e54c4ea..4a2455d 100644
--- a/n.h
+++ b/n.h
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <assert.h>
+#include <stdarg.h>
 /* extra includes */
 #include <math.h>
 #include <errno.h>
diff --git a/s.h b/s.h
index c7bbcaa..21052df 100644
--- a/s.h
+++ b/s.h
@@ -24,6 +24,7 @@
 #include <stdio.h>
 #include <wchar.h>
 #include <assert.h>
+#include <stdarg.h>
 
 #if defined(_MSC_VER)
 #ifdef _POSIX_