diff --git a/zconf.h b/zconf.h
index 254d7b53a0e1d054e5a53710752e9043235e698e..57f25adafd93193796ac81e44b0dd3770fbc6faf 100644
--- a/zconf.h
+++ b/zconf.h
@@ -439,11 +439,11 @@ typedef uLong FAR uLongf;
 #if !defined(_WIN32) && (defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0)
 #  define z_off64_t off64_t
 #else
-#  if defined(_WIN32)
+#  if defined(_WIN32) && !defined(__GNUC__) && !defined(Z_SOLO)
 #    define z_off64_t __int64
 #  else
-#  define z_off64_t z_off_t
-#endif
+#    define z_off64_t z_off_t
+#  endif
 #endif
 
 /* MVS linker does not support external names larger than 8 bytes */
diff --git a/zconf.h.cmakein b/zconf.h.cmakein
index 8109100c32591fd78a802c69ed93fe29bdce3667..dd2d28a41295f4e507de8cbeaf7acc131de93f02 100644
--- a/zconf.h.cmakein
+++ b/zconf.h.cmakein
@@ -441,11 +441,11 @@ typedef uLong FAR uLongf;
 #if !defined(_WIN32) && (defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0)
 #  define z_off64_t off64_t
 #else
-#  if defined(_WIN32)
+#  if defined(_WIN32) && !defined(__GNUC__) && !defined(Z_SOLO)
 #    define z_off64_t __int64
 #  else
-#  define z_off64_t z_off_t
-#endif
+#    define z_off64_t z_off_t
+#  endif
 #endif
 
 /* MVS linker does not support external names larger than 8 bytes */
diff --git a/zconf.h.in b/zconf.h.in
index 254d7b53a0e1d054e5a53710752e9043235e698e..57f25adafd93193796ac81e44b0dd3770fbc6faf 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -439,11 +439,11 @@ typedef uLong FAR uLongf;
 #if !defined(_WIN32) && (defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0)
 #  define z_off64_t off64_t
 #else
-#  if defined(_WIN32)
+#  if defined(_WIN32) && !defined(__GNUC__) && !defined(Z_SOLO)
 #    define z_off64_t __int64
 #  else
-#  define z_off64_t z_off_t
-#endif
+#    define z_off64_t z_off_t
+#  endif
 #endif
 
 /* MVS linker does not support external names larger than 8 bytes */