diff --git a/code/Common/ZipArchiveIOSystem.cpp b/code/Common/ZipArchiveIOSystem.cpp
index e0c9883d2..c748b3255 100644
--- a/code/Common/ZipArchiveIOSystem.cpp
+++ b/code/Common/ZipArchiveIOSystem.cpp
@@ -196,7 +196,9 @@ zlib_filefunc_def IOSystem2Unzip::get(IOSystem *pIOHandler) {
     zlib_filefunc_def mapping;
 
     mapping.zopen_file = (open_file_func)open;
+#ifdef ZOPENDISK64
     mapping.zopendisk_file = (opendisk_file_func)opendisk;
+#endif
     mapping.zread_file = (read_file_func)read;
     mapping.zwrite_file = (write_file_func)write;
     mapping.ztell_file = (tell_file_func)tell;
