diff --git a/mkfiles.pl b/mkfiles.pl
index b38a218b..7cb42fb6 100755
--- a/mkfiles.pl
+++ b/mkfiles.pl
@@ -1155,7 +1155,7 @@ if (defined $makefiles{'am'}) {
       $objtosrc{$d->{obj}} = $d->{deps}->[0];
     }
 
-    @amcflags = ("\$(COMPAT)", "\$(XFLAGS)", map {"-I$dirpfx$_"} @srcdirs);
+    @amcflags = ("\$(COMPAT)", "\$(XFLAGS)", "\$(WARNINGOPTS)", map {"-I$dirpfx$_"} @srcdirs);
     print "if HAVE_GTK\n";
     print &splitline(join " ", "AM_CFLAGS", "=",
                      "\$(GTK_CFLAGS)", @amcflags), "\n";
diff --git a/unix/configure.ac b/unix/configure.ac
index 930f3e37..f9fe51fe 100644
--- a/unix/configure.ac
+++ b/unix/configure.ac
@@ -122,6 +122,14 @@ AC_CHECK_FUNCS([getaddrinfo ptsname setresuid strsignal updwtmpx])
 AC_CHECK_DECLS([CLOCK_MONOTONIC], [], [], [[#include <time.h>]])
 AC_SEARCH_LIBS([clock_gettime], [rt], [AC_DEFINE([HAVE_CLOCK_GETTIME],[],[Define if clock_gettime() is available])])
 
+if test "x$GCC" = "xyes"; then
+  :
+  AC_SUBST(WARNINGOPTS, ['-Wall -Werror'])
+else
+  :
+  AC_SUBST(WARNINGOPTS, [])
+fi
+
 AC_OUTPUT
 
 if test "$gtk_version_desired" = "no"; then cat <<EOF