diff --git a/configure.ac b/configure.ac
index 012fbd3fb..ae649b4a0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -346,6 +346,10 @@ dnl ############################################################################
 dnl OS specific stuff
 dnl ############################################################################
 
+AC_CHECK_DECLS([environ], , ,
+  [ #include <unistd.h>
+    #include <stdlib.h> ])
+
 case $host_os in
 *os400)
     AC_PATH_PROG([PERL], [perl], [/QOpenSys/pkgs/bin/perl])
diff --git a/lib/widget/input_complete.c b/lib/widget/input_complete.c
index cd0ccbc87..4d3fd8b4b 100644
--- a/lib/widget/input_complete.c
+++ b/lib/widget/input_complete.c
@@ -54,8 +54,7 @@
 
 /*** global variables ****************************************************************************/
 
-/* Linux declares environ in <unistd.h>, so don't repeat it here. */
-#if (!(defined(__linux__) && defined (__USE_GNU)) && !defined(__CYGWIN__))
+#if !HAVE_DECL_ENVIRON
 extern char **environ;
 #endif