diff --git a/zconf.h b/zconf.h
index ad82e3b..254d7b5 100644
--- a/zconf.h
+++ b/zconf.h
@@ -413,7 +413,7 @@ typedef uLong FAR uLongf;
 #  define Z_LARGE
 #endif
 
-#if defined(__WATCOM__) && !defined(Z_HAVE_UNISTD_H)
+#if defined(__WATCOMC__) && !defined(Z_HAVE_UNISTD_H)
 #  define Z_HAVE_UNISTD_H
 #endif
 #if (defined(Z_HAVE_UNISTD_H) || defined(Z_LARGE)) && !defined(Z_SOLO)
diff --git a/zconf.h.cmakein b/zconf.h.cmakein
index 6f964b8..8109100 100644
--- a/zconf.h.cmakein
+++ b/zconf.h.cmakein
@@ -415,7 +415,7 @@ typedef uLong FAR uLongf;
 #  define Z_LARGE
 #endif
 
-#if defined(__WATCOM__) && !defined(Z_HAVE_UNISTD_H)
+#if defined(__WATCOMC__) && !defined(Z_HAVE_UNISTD_H)
 #  define Z_HAVE_UNISTD_H
 #endif
 #if (defined(Z_HAVE_UNISTD_H) || defined(Z_LARGE)) && !defined(Z_SOLO)
diff --git a/zconf.h.in b/zconf.h.in
index ad82e3b..254d7b5 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -413,7 +413,7 @@ typedef uLong FAR uLongf;
 #  define Z_LARGE
 #endif
 
-#if defined(__WATCOM__) && !defined(Z_HAVE_UNISTD_H)
+#if defined(__WATCOMC__) && !defined(Z_HAVE_UNISTD_H)
 #  define Z_HAVE_UNISTD_H
 #endif
 #if (defined(Z_HAVE_UNISTD_H) || defined(Z_LARGE)) && !defined(Z_SOLO)