Fixup include of stdarg and va_list definition.
diff --git a/py/misc.h b/py/misc.h
index 15a8805..4a100af 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -83,7 +83,10 @@
 //void vstr_add_le32(vstr_t *vstr, unsigned int v);
 void vstr_cut_tail(vstr_t *vstr, int len);
 void vstr_printf(vstr_t *vstr, const char *fmt, ...);
+
+#ifdef va_start
 void vstr_vprintf(vstr_t *vstr, const char *fmt, va_list ap);
+#endif
 
 /** unique string ***********************************************/