diff --git a/postfix-3.5.9-glibc-234-build-fix.patch b/postfix-3.5.9-glibc-234-build-fix.patch
new file mode 100644
index 0000000..71ea284
--- /dev/null
+++ b/postfix-3.5.9-glibc-234-build-fix.patch
@@ -0,0 +1,43 @@
+diff --git a/src/util/sys_compat.c b/src/util/sys_compat.c
+index 8bf8e58..c87f043 100644
+--- a/src/util/sys_compat.c
++++ b/src/util/sys_compat.c
+@@ -286,7 +286,7 @@ int     dup2_pass_on_exec(int oldd, int newd)
+ 
+ /* closefrom() - closes all file descriptors from the given one up */
+ 
+-int     closefrom(int lowfd)
++void     closefrom(int lowfd)
+ {
+     int     fd_limit = open_limit(0);
+     int     fd;
+@@ -298,14 +298,14 @@ int     closefrom(int lowfd)
+      */
+     if (lowfd < 0) {
+ 	errno = EBADF;
+-	return (-1);
++	return;
+     }
+     if (fd_limit > 500)
+ 	fd_limit = 500;
+     for (fd = lowfd; fd < fd_limit; fd++)
+ 	(void) close(fd);
+ 
+-    return (0);
++    return;
+ }
+ 
+ #endif
+diff --git a/src/util/sys_defs.h b/src/util/sys_defs.h
+index 99bec9b..16e27db 100644
+--- a/src/util/sys_defs.h
++++ b/src/util/sys_defs.h
+@@ -1509,7 +1509,7 @@ extern int setsid(void);
+ #endif
+ 
+ #ifndef HAS_CLOSEFROM
+-extern int closefrom(int);
++extern void closefrom(int);
+ 
+ #endif
+ 
diff --git a/postfix.spec b/postfix.spec
index 1fa55d0..bbc7a4d 100644
--- a/postfix.spec
+++ b/postfix.spec
@@ -49,7 +49,7 @@
 Name: postfix
 Summary: Postfix Mail Transport Agent
 Version: 3.5.9
-Release: 10%{?dist}
+Release: 11%{?dist}
 Epoch: 2
 URL: http://www.postfix.org
 License: (IBM and GPLv2+) or (EPL-2.0 and GPLv2+)
@@ -94,6 +94,8 @@ Patch9: pflogsumm-1.1.5-datecalc.patch
 # rhbz#1384871, sent upstream
 Patch10: pflogsumm-1.1.5-ipv6-warnings-fix.patch
 Patch11: postfix-3.4.4-chroot-example-fix.patch
+# reported upstream
+Patch12: postfix-3.5.9-glibc-234-build-fix.patch
 
 # Optional patches - set the appropriate environment variables to include
 #                    them when building the package/spec file
@@ -244,6 +246,7 @@ pushd pflogsumm-%{pflogsumm_ver}
 popd
 %endif
 %patch11 -p1 -b .chroot-example-fix
+%patch12 -p1 -b .glibc-234-build-fix
 
 for f in README_FILES/TLS_{LEGACY_,}README TLS_ACKNOWLEDGEMENTS; do
 	iconv -f iso8859-1 -t utf8 -o ${f}{_,} &&
@@ -787,6 +790,10 @@ fi
 %endif
 
 %changelog
+* Tue Aug  3 2021 Jaroslav Škarvada <jskarvad@redhat.com> - 2:3.5.9-11
+- Fixed FTBFS with glibc-2.34
+  Resolves: rhbz#1984045
+
 * Mon Aug  2 2021 Jaroslav Škarvada <jskarvad@redhat.com> - 2:3.5.9-10
 - Fixed scriptlets to work with openssl-3.0
   Resolves: rhbz#1985918