Index: src/libical/icaltz-util.c
--- src/libical/icaltz-util.c.orig
+++ src/libical/icaltz-util.c
@@ -49,8 +49,13 @@
 #endif
 #endif
 
-#if defined(__OpenBSD__) && !defined(bswap_32)
+#if defined(__OpenBSD__)
+#if !defined(bswap_32)
 #define bswap_32 swap32
+#endif
+#if !defined(bswap_64)
+#define bswap_64 swap64
+#endif
 #endif
 
 #if defined(_MSC_VER)