diff --git a/backport-rcs-5.9.4-SIGSTKSZ.patch b/backport-rcs-5.9.4-SIGSTKSZ.patch
new file mode 100644
index 0000000..3a55cbb
--- /dev/null
+++ b/backport-rcs-5.9.4-SIGSTKSZ.patch
@@ -0,0 +1,33 @@
+diff --git a/src/b-isr.c b/src/b-isr.c
+index 52c3a6f..d839631 100644
+--- a/src/b-isr.c
++++ b/src/b-isr.c
+@@ -195,22 +195,16 @@ setup_catchsig (size_t count, int const set[VLA_ELEMS (count)])
+ #undef MUST
+ }
+ 
+-#if defined HAVE_SIGALTSTACK && defined SIGSTKSZ
+-#define ISR_STACK_SIZE  (10 * SIGSTKSZ)
+-#else
+-#define ISR_STACK_SIZE  0
+-#endif
+-
+ struct isr_scratch *
+ isr_init (bool *be_quiet)
+ {
+   struct isr_scratch *scratch = ZLLOC (1, struct isr_scratch);
+ 
+-#if ISR_STACK_SIZE
++#if defined HAVE_SIGALTSTACK && defined SIGSTKSZ
+   stack_t ss =
+     {
+-      .ss_sp = alloc (PLEXUS, "sigaltstack", ISR_STACK_SIZE),
+-      .ss_size = ISR_STACK_SIZE,
++     .ss_sp = alloc (PLEXUS, "sigaltstack", (10 * SIGSTKSZ)),
++      .ss_size = (10 * SIGSTKSZ),
+       .ss_flags = 0
+     };
+ 
+-- 
+1.8.3.1
+
diff --git a/rcs.spec b/rcs.spec
index 411f6d8..b049f43 100644
--- a/rcs.spec
+++ b/rcs.spec
@@ -1,12 +1,13 @@
 Summary: Revision Control System (RCS) file version management tools
 Name: rcs
 Version: 5.9.4
-Release: 12
+Release: 13
 License: GPLv3+
 URL: http://www.gnu.org/software/rcs/
 Source: ftp://ftp.gnu.org/gnu/rcs/%{name}-%{version}.tar.xz
 Patch0: rcs-5.8-build-tweaks.patch
 Patch1: rcs-5.9.4-t810_disable.patch
+Patch6000: backport-rcs-5.9.4-SIGSTKSZ.patch
 
 Provides: bundled(gnulib)
 BuildRequires:  gcc autoconf groff ghostscript ed texinfo
@@ -62,6 +63,9 @@ fi
 %{_mandir}/man[15]/*
 
 %changelog
+* Tue Aug 10 2021 shixuantong <shixuantong@huawei.com> - 5.9.4-13
+- fix build fail for SIGSTKSZ
+
 * Mon Jun 28 2021 shangyibin <shangyibin1@openeuler.org> - 5.9.4-12
 - %perp no longer patched with git