diff --git a/clisp-c99.patch b/clisp-c99.patch
new file mode 100644
index 0000000..9e86315
--- /dev/null
+++ b/clisp-c99.patch
@@ -0,0 +1,36 @@
+berkeley-db: Avoid failure of HAVE_DB_STAT_ACCEPT_TXN test in
+configure
+
+The last argument for db_stat is of type uint32_t, and compilers may
+not allow passing NULL in its place.  This causes the check to fail
+in some cases where HAVE_DB_STAT_ACCEPT_TXN is expected to be defined,
+leading to build failures later.
+
+Submitted upstream: <https://gitlab.com/gnu-clisp/clisp/-/merge_requests/8>
+
+diff --git modules/berkeley-db/configure modules/berkeley-db/configure
+index 6f63e605b..c8734a1ca 100755
+--- modules/berkeley-db/configure
++++ modules/berkeley-db/configure
+@@ -6347,7 +6347,7 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+ int
+ main (void)
+ {
+-DB db; db.stat(&db,NULL,0,NULL);
++DB db; db.stat(&db,NULL,0,0);
+   ;
+   return 0;
+ }
+diff --git modules/berkeley-db/configure.in modules/berkeley-db/configure.in
+index c2b8a5d2d..225fd91b1 100644
+--- modules/berkeley-db/configure.in
++++ modules/berkeley-db/configure.in
+@@ -38,7 +38,7 @@ AC_CHECK_SIZEOF(db_recno_t,,[#include <stdio.h>
+ dnl <http://www.sleepycat.com/docs/ref/upgrade.4.3/stat.html>
+ AC_CACHE_CHECK([whether DB->stat() accepts TXNid],ac_cv_db_stat_accept_txn,[
+ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <db.h>],
+-[[DB db; db.stat(&db,NULL,0,NULL);]])],
++[[DB db; db.stat(&db,NULL,0,0);]])],
+ ac_cv_db_stat_accept_txn=yes,ac_cv_db_stat_accept_txn=no)])
+ if test "$ac_cv_db_stat_accept_txn" = "yes"; then
+ AC_DEFINE(HAVE_DB_STAT_ACCEPT_TXN,1,[Define to 1 if DB->stat() accepts TXNid])
diff --git a/clisp.spec b/clisp.spec
index d140106..b0cb2c5 100644
--- a/clisp.spec
+++ b/clisp.spec
@@ -26,7 +26,7 @@ Version:	2.49.93
 # - src/socket.d and modules/clx/mit-clx/doc.lisp are HPND
 # - src/xthread.d and modules/asdf/asdf.lisp are X11
 License:	GPL-2.0-or-later AND (GPL-2.0-or-later OR GFDL-1.2-or-later) AND LGPL-2.1-or-later AND HPND AND X11
-Release:	30%{?dist}
+Release:	31%{?dist}
 URL:		http://www.clisp.org/
 Source0:	%{forgesource}
 # Upstream dropped this file from the distribution
@@ -45,9 +45,11 @@ Patch2:		%{name}-register-volatile.patch
 # Perhaps we are racing with something else that allocates a pty.  Disable
 # the test for now.
 Patch3:         %{name}-pts-access.patch
+Patch4:         clisp-c99.patch
+
 # Work around a problem inlining a function on ppc64le
 # See https://bugzilla.redhat.com/show_bug.cgi?id=2049371
-Patch4:         %{name}-no-inline.patch
+Patch100:         %{name}-no-inline.patch
 
 BuildRequires:	dbus-devel
 BuildRequires:	diffutils
@@ -123,9 +125,9 @@ Files necessary for linking CLISP programs.
 
 %prep
 %forgesetup
-%autopatch -M4 -p0
+%autopatch -M99 -p0
 %ifarch %{power64}
-%autopatch 5 -p0
+%autopatch 100 -p0
 %endif
 cp -p %{SOURCE1} emacs
 cp -p %{SOURCE2} %{SOURCE3} src/po
@@ -454,6 +456,9 @@ make -C build base-mod-check
 
 
 %changelog
+* Mon May 08 2023 Florian Weimer <fweimer@redhat.com> - 2.49.93-31
+- Port to C99
+
 * Tue Apr  4 2023 Jerry James <loganjerry@gmail.com> - 2.49.93-30
 - Update to allow non-simple strings in FORMAT and FORMATTER
 - Drop upstreamed ensure-6x patch