diff --git a/libz/zconf.h b/libz/zconf.h
index 77398c11a..5e1d68a00 100644
--- a/libz/zconf.h
+++ b/libz/zconf.h
@@ -431,11 +431,11 @@ typedef uLong FAR uLongf;
    typedef unsigned long z_crc_t;
 #endif
 
-#if 1    /* was set to #if 1 by ./configure */
+#ifdef HAVE_UNISTD_H    /* may be set to #if 1 by ./configure */
 #  define Z_HAVE_UNISTD_H
 #endif
 
-#if 1    /* was set to #if 1 by ./configure */
+#ifdef HAVE_STDARG_H    /* may be set to #if 1 by ./configure */
 #  define Z_HAVE_STDARG_H
 #endif