diff --git a/hwaccess.h b/hwaccess.h
index 53e908a..c38ee6f 100644
--- a/hwaccess.h
+++ b/hwaccess.h
@@ -228,17 +228,25 @@
 #endif
 #endif
 
-#if defined(__NetBSD__)
+#if defined(__NetBSD__) || defined (__OpenBSD__)
   #define off64_t off_t
   #define lseek64 lseek
   #if defined(__i386__) || defined(__x86_64__)
     #include <sys/types.h>
     #include <machine/sysarch.h>
+#if defined(__NetBSD__)
     #if defined(__i386__)
       #define iopl i386_iopl
     #elif defined(__x86_64__)
       #define iopl x86_64_iopl
     #endif
+#elif defined (__OpenBSD__)
+    #if defined(__i386__)
+      #define iopl i386_iopl
+    #elif defined(__amd64__)
+      #define iopl amd64_iopl
+    #endif
+#endif
   #include <stdint.h>
 
 static inline void outb(uint8_t value, uint16_t port)