--- a/zlib.h
+++ b/zlib.h
@@ -1563,12 +1563,7 @@ ZEXTERN int ZEXPORT inflateBackInit_ OF(
  * without large file support, _LFS64_LARGEFILE must also be true
  */
 #if defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0
-   ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
-   ZEXTERN z_off64_t ZEXPORT gzseek64 OF((gzFile, z_off64_t, int));
-   ZEXTERN z_off64_t ZEXPORT gztell64 OF((gzFile));
-   ZEXTERN z_off64_t ZEXPORT gzoffset64 OF((gzFile));
-   ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off64_t));
-   ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off64_t));
+  #define __zlib_largefile64
 #endif
 
 #if !defined(ZLIB_INTERNAL) && _FILE_OFFSET_BITS-0 == 64 && _LFS64_LARGEFILE-0
@@ -1578,13 +1573,8 @@ ZEXTERN int ZEXPORT inflateBackInit_ OF(
 #  define gzoffset gzoffset64
 #  define adler32_combine adler32_combine64
 #  define crc32_combine crc32_combine64
-#  ifdef _LARGEFILE64_SOURCE
-     ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
-     ZEXTERN z_off_t ZEXPORT gzseek64 OF((gzFile, z_off_t, int));
-     ZEXTERN z_off_t ZEXPORT gztell64 OF((gzFile));
-     ZEXTERN z_off_t ZEXPORT gzoffset64 OF((gzFile));
-     ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off_t));
-     ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off_t));
+#  ifndef __zlib_largefile64
+#    define __zlib_largefile64
 #  endif
 #else
    ZEXTERN gzFile ZEXPORT gzopen OF((const char *, const char *));
@@ -1595,6 +1585,15 @@ ZEXTERN int ZEXPORT inflateBackInit_ OF(
    ZEXTERN uLong ZEXPORT crc32_combine OF((uLong, uLong, z_off_t));
 #endif
 
+#ifdef __zlib_largefile64
+   ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
+   ZEXTERN z_off64_t ZEXPORT gzseek64 OF((gzFile, z_off64_t, int));
+   ZEXTERN z_off64_t ZEXPORT gztell64 OF((gzFile));
+   ZEXTERN z_off64_t ZEXPORT gzoffset64 OF((gzFile));
+   ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off64_t));
+   ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off64_t));
+#endif
+
 /* hack for buggy compilers */
 #if !defined(ZUTIL_H) && !defined(NO_DUMMY_DECL)
     struct internal_state {int dummy;};
