diff --git a/zconf.h b/zconf.h
index 62adc8d..0a9f22c 100644
--- a/zconf.h
+++ b/zconf.h
@@ -470,12 +470,8 @@ typedef uLong FAR uLongf;
 #endif
 
 #ifndef Z_HAVE_UNISTD_H
-#  ifdef __WATCOMC__
-#    define Z_HAVE_UNISTD_H
-#  endif
-#endif
-#ifndef Z_HAVE_UNISTD_H
-#  if defined(_LARGEFILE64_SOURCE) && !defined(_WIN32)
+#  if defined(__WATCOMC__) || defined(__GO32__) || \
+      (defined(_LARGEFILE64_SOURCE) && !defined(_WIN32))
 #    define Z_HAVE_UNISTD_H
 #  endif
 #endif
diff --git a/zconf.h.cmakein b/zconf.h.cmakein
index 0abe3bc..a5cb288 100644
--- a/zconf.h.cmakein
+++ b/zconf.h.cmakein
@@ -472,12 +472,8 @@ typedef uLong FAR uLongf;
 #endif
 
 #ifndef Z_HAVE_UNISTD_H
-#  ifdef __WATCOMC__
-#    define Z_HAVE_UNISTD_H
-#  endif
-#endif
-#ifndef Z_HAVE_UNISTD_H
-#  if defined(_LARGEFILE64_SOURCE) && !defined(_WIN32)
+#  if defined(__WATCOMC__) || defined(__GO32__) || \
+      (defined(_LARGEFILE64_SOURCE) && !defined(_WIN32))
 #    define Z_HAVE_UNISTD_H
 #  endif
 #endif
diff --git a/zconf.h.in b/zconf.h.in
index 62adc8d..0a9f22c 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -470,12 +470,8 @@ typedef uLong FAR uLongf;
 #endif
 
 #ifndef Z_HAVE_UNISTD_H
-#  ifdef __WATCOMC__
-#    define Z_HAVE_UNISTD_H
-#  endif
-#endif
-#ifndef Z_HAVE_UNISTD_H
-#  if defined(_LARGEFILE64_SOURCE) && !defined(_WIN32)
+#  if defined(__WATCOMC__) || defined(__GO32__) || \
+      (defined(_LARGEFILE64_SOURCE) && !defined(_WIN32))
 #    define Z_HAVE_UNISTD_H
 #  endif
 #endif