diff --git a/shellinabox-configure-c99.patch b/shellinabox-configure-c99.patch
new file mode 100644
index 0000000..382dbbd
--- /dev/null
+++ b/shellinabox-configure-c99.patch
@@ -0,0 +1,21 @@
+Define _GNU_SOURCE when probing for updwtmpx.  Otherwise, glibc's
+<utmpx.h> will not declare this function, and the configure probe
+fails with compilers which do not support implicit function
+declarations.
+
+Submitted upstream: <https://github.com/shellinabox/shellinabox/pull/514>
+
+diff --git a/configure.ac b/configure.ac
+index 56e3b6a2b510851f..d05d1216dd4a397f 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -154,7 +154,8 @@ if test "x$enable_utmp" != xno; then
+               [updwtmp(0, 0);],
+               [AC_DEFINE(HAVE_UPDWTMP, 1,
+                          Define to 1 if you have support for updwtmp)])
+-  AC_TRY_LINK([#include <utmpx.h>],
++  AC_TRY_LINK([#define _GNU_SOURCE
++	      #include <utmpx.h>],
+               [updwtmpx(0, 0);],
+               [AC_DEFINE(HAVE_UPDWTMPX, 1,
+                          Define to 1 if you have support for updwtmpx)])
diff --git a/shellinabox.spec b/shellinabox.spec
index e82e640..45af159 100644
--- a/shellinabox.spec
+++ b/shellinabox.spec
@@ -2,9 +2,10 @@
 
 Name:           shellinabox
 Version:        2.20
-Release:        19%{?dist}
+Release:        27%{?dist}
 Summary:        Web based AJAX terminal emulator
-License:        GPLv2
+# Automatically converted from old format: GPLv2 - review is highly recommended.
+License:        GPL-2.0-only
 URL:            https://github.com/%{name}/%{name}
 
 Source0:        https://github.com/%{name}/%{name}/archive/v%{version}.tar.gz#/%{name}-%{version}.tar.gz
@@ -14,6 +15,7 @@ Source3:        shellinaboxd.init
 
 Patch0:         %{name}-ssh-options.patch
 Patch1:         %{name}-gcc11.patch
+Patch2: shellinabox-configure-c99.patch
 
 BuildRequires: make
 BuildRequires:  autoconf
@@ -23,7 +25,6 @@ BuildRequires:  openssl-devel
 BuildRequires:  zlib-devel
 
 Requires:       openssl
-Requires(pre):  shadow-utils
 
 %if 0%{?fedora} || 0%{?rhel} >= 7
 BuildRequires:      systemd
@@ -47,8 +48,14 @@ browser plugins.
 
 %prep
 %setup -q
-%patch0 -p1
-%patch1 -p1
+%patch -P0 -p1
+%patch -P1 -p1
+%patch -P2 -p1
+
+# Create a sysusers.d config file
+cat >shellinabox.sysusers.conf <<EOF
+u shellinabox - 'Shellinabox' %{_sharedstatedir}/shellinabox -
+EOF
 
 %build
 autoreconf -vif
@@ -79,12 +86,9 @@ install -p -m 755 -D %{SOURCE3} %{buildroot}%{_initrddir}/shellinaboxd
 
 %endif
 
-%pre
-getent group %username >/dev/null || groupadd -r %username &>/dev/null || :
-getent passwd %username >/dev/null || useradd -r -s /sbin/nologin \
-    -d %{_sharedstatedir}/shellinabox -M -c 'Shellinabox' -g %username %username &>/dev/null || :
-exit 0
+install -m0644 -D shellinabox.sysusers.conf %{buildroot}%{_sysusersdir}/shellinabox.conf
 
+%pre
 %if 0%{?fedora} || 0%{?rhel} >= 7
 
 %post
@@ -131,8 +135,33 @@ fi
 %{_initrddir}/shellinaboxd
 %endif
 %attr(750,%{username},%{username}) %{_sharedstatedir}/%{name}
+%{_sysusersdir}/shellinabox.conf
 
 %changelog
+* Fri Jul 25 2025 Fedora Release Engineering <releng@fedoraproject.org> - 2.20-27
+- Rebuilt for https://fedoraproject.org/wiki/Fedora_43_Mass_Rebuild
+
+* Tue Feb 11 2025 Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> - 2.20-26
+- Add sysusers.d config file to allow rpm to create users/groups automatically
+
+* Sun Jan 19 2025 Fedora Release Engineering <releng@fedoraproject.org> - 2.20-25
+- Rebuilt for https://fedoraproject.org/wiki/Fedora_42_Mass_Rebuild
+
+* Mon Jul 29 2024 Miroslav Suchý <msuchy@redhat.com> - 2.20-24
+- convert license to SPDX
+
+* Sat Jul 20 2024 Fedora Release Engineering <releng@fedoraproject.org> - 2.20-23
+- Rebuilt for https://fedoraproject.org/wiki/Fedora_41_Mass_Rebuild
+
+* Sat Jan 27 2024 Fedora Release Engineering <releng@fedoraproject.org> - 2.20-22
+- Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild
+
+* Sat Jul 22 2023 Fedora Release Engineering <releng@fedoraproject.org> - 2.20-21
+- Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild
+
+* Wed Apr 26 2023 Florian Weimer <fweimer@redhat.com> - 2.20-20
+- Port configure script to C99
+
 * Sat Jan 21 2023 Fedora Release Engineering <releng@fedoraproject.org> - 2.20-19
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_38_Mass_Rebuild