Index: gcc/d/dmd/root/port.h
--- gcc/d/dmd/root/port.h.orig
+++ gcc/d/dmd/root/port.h
@@ -32,4 +32,7 @@ struct Port
     static unsigned readwordLE(const void *buffer);
     static unsigned readwordBE(const void *buffer);
     static void valcpy(void *dst, uint64_t val, d_size_t size);
+#if defined(__OpenBSD__) && defined(__LP64__)
+    static void valcpy(void *dst, unsigned long val, size_t size);
+#endif
 };
