diff --git a/lib/zlib/zconf.h b/lib/zlib/zconf.h
index bf977d3..fb76ffe 100644
--- a/lib/zlib/zconf.h
+++ b/lib/zlib/zconf.h
@@ -241,7 +241,11 @@
 #endif
 
 #ifdef Z_SOLO
-   typedef unsigned long z_size_t;
+#  ifdef _WIN64
+     typedef unsigned long long z_size_t;
+#  else
+     typedef unsigned long z_size_t;
+#  endif
 #else
 #  define z_longlong long long
 #  if defined(NO_SIZE_T)
@@ -520,7 +524,7 @@
 #if !defined(_WIN32) && defined(Z_LARGE64)
 #  define z_off64_t off64_t
 #else
-#  if defined(_WIN32) && !defined(__GNUC__) && !defined(Z_SOLO)
+#  if defined(_WIN32) && !defined(__GNUC__)
 #    define z_off64_t __int64
 #  else
 #    define z_off64_t z_off_t