diff --git a/src/sim65/paravirt.c b/src/sim65/paravirt.c
index fda2839af..1c431fdc9 100644
--- a/src/sim65/paravirt.c
+++ b/src/sim65/paravirt.c
@@ -48,6 +48,12 @@
 /* Anyone else */
 #  include <unistd.h>
 #endif
+#ifndef S_IREAD
+#  define S_IREAD  S_IRUSR
+#endif
+#ifndef S_IWRITE
+#  define S_IWRITE S_IWUSR
+#endif
 
 /* common */
 #include "cmdline.h"