diff --git a/lib/kafs/afssysdefs.h b/lib/kafs/afssysdefs.h
index e0c696076..a20e7bcf4 100644
--- a/lib/kafs/afssysdefs.h
+++ b/lib/kafs/afssysdefs.h
@@ -91,8 +91,10 @@
 #endif /* __FreeBSD__ */
 
 #ifdef __DragonFly__
+#ifndef AFS_SYSCALL
 #define AFS_SYSCALL 339
 #endif
+#endif
 
 #ifdef __OpenBSD__
 #define AFS_SYSCALL 208