diff --git a/sudo-configure-c99.patch b/sudo-configure-c99.patch
new file mode 100644
index 0000000..69a0cd2
--- /dev/null
+++ b/sudo-configure-c99.patch
@@ -0,0 +1,65 @@
+Avoid implicit function declarations, so that the configure probe
+results do not change with future compilers.
+
+Submitted upstream for discussion:
+
+  <https://www.sudo.ws/pipermail/sudo-workers/2023-April/001387.html>
+
+
+diff --git a/configure b/configure
+index d406eb77a22d3c3c..29483788443d2b21 100755
+--- a/configure
++++ b/configure
+@@ -31220,10 +31220,13 @@ else case e in #(
+ /* end confdefs.h.  */
+ #include <sys/types.h>
+ #include <ldap.h>
++
++void *volatile ptr;
++
+ int
+ main (void)
+ {
+-(void)ldap_init(0, 0)
++ptr = (void *) ldap_msgfree
+   ;
+   return 0;
+ }
+@@ -33914,7 +33917,7 @@ then :
+ else case e in #(
+   e) cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+ /* end confdefs.h.  */
+-
++#include <stdio.h>
+ 
+ int
+ main (void)
+diff --git a/m4/hardening.m4 b/m4/hardening.m4
+index f7d2a8c2911ed9d6..1ebfd9fdaf461285 100644
+--- a/m4/hardening.m4
++++ b/m4/hardening.m4
+@@ -10,7 +10,7 @@ AC_DEFUN([SUDO_CHECK_HARDENING], [
+ 	    [sudo_cv_use_fortify_source],
+ 	    [AC_LINK_IFELSE([
+ 		    AC_LANG_PROGRAM(
+-			[[]], [[char buf[4]; (void)sprintf(buf, "%s", "foo");]]
++			[[#include <string.h>]], [[char buf[4]; (void)sprintf(buf, "%s", "foo");]]
+ 		    )],
+ 		    [sudo_cv_use_fortify_source=yes],
+ 		    [sudo_cv_use_fortify_source=no]
+diff --git a/m4/ldap.m4 b/m4/ldap.m4
+index 78c21e0bc0a1f65f..a6361df044d84f92 100644
+--- a/m4/ldap.m4
++++ b/m4/ldap.m4
+@@ -52,7 +52,10 @@ AC_DEFUN([SUDO_CHECK_LDAP], [
+ #include <lber.h>])
+ 	AC_CACHE_CHECK([whether lber.h is needed when including ldap.h], [sudo_cv_header_lber_h], [
+ 	    AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <sys/types.h>
+-#include <ldap.h>]], [[(void)ldap_init(0, 0)]])], [
++#include <ldap.h>
++
++void *volatile ptr;
++]], [[ptr = (void *) ldap_msgfree]])], [
+ 		# No need to explicitly include lber.h when including ldap.h.
+ 		sudo_cv_header_lber_h=no
+ 	    ], [
diff --git a/sudo.spec b/sudo.spec
index 7a10271..315ea49 100644
--- a/sudo.spec
+++ b/sudo.spec
@@ -13,6 +13,7 @@ License: ISC
 URL: https://www.sudo.ws
 Source0: %{url}/dist/%{name}-%{version}%{?extraver}.tar.gz
 Source1: sudoers
+Patch0: sudo-configure-c99.patch
 Requires: pam
 Recommends: system-default-editor
 Recommends: %{name}-python-plugin%{?_isa} = %{version}-%{release}
@@ -70,7 +71,7 @@ BuildRequires:  python3-devel
 %{name}-python-plugin allows using sudo plugins written in Python.
 
 %prep
-%setup -q -n %{name}-%{version}%{?extraver}
+%autosetup -p1 -n %{name}-%{version}%{?extraver}
 
 %build
 # Remove bundled copy of zlib