diff --git a/src/libos/src/signal/syscalls.rs b/src/libos/src/signal/syscalls.rs
index 76672b6f..7e6507be 100644
--- a/src/libos/src/signal/syscalls.rs
+++ b/src/libos/src/signal/syscalls.rs
@@ -14,9 +14,15 @@ pub fn do_rt_sigaction(
     signum_c: c_int,
     new_sa_c: *const sigaction_t,
     old_sa_c: *mut sigaction_t,
+    sigset_size: size_t,
 ) -> Result<isize> {
     // C types -> Rust types
     let signum = SigNum::from_u8(signum_c as u8)?;
+
+    if sigset_size != std::mem::size_of::<sigset_t>() {
+        return_errno!(EINVAL, "unexpected sig action size");
+    }
+
     let new_sa = {
         if !new_sa_c.is_null() {
             let new_sa_c = unsafe { &*new_sa_c };
diff --git a/src/libos/src/syscall/mod.rs b/src/libos/src/syscall/mod.rs
index 3c0ee5ed..6bbd379d 100644
--- a/src/libos/src/syscall/mod.rs
+++ b/src/libos/src/syscall/mod.rs
@@ -110,7 +110,7 @@ macro_rules! process_syscall_table_with_callback {
             (Mprotect = 10) => do_mprotect(addr: usize, len: usize, prot: u32),
             (Munmap = 11) => do_munmap(addr: usize, size: usize),
             (Brk = 12) => do_brk(new_brk_addr: usize),
-            (RtSigaction = 13) => do_rt_sigaction(signum_c: c_int, new_sa_c: *const sigaction_t, old_sa_c: *mut sigaction_t),
+            (RtSigaction = 13) => do_rt_sigaction(signum_c: c_int, new_sa_c: *const sigaction_t, old_sa_c: *mut sigaction_t, sigset_size: size_t),
             (RtSigprocmask = 14) => do_rt_sigprocmask(how: c_int, set: *const sigset_t, oldset: *mut sigset_t, sigset_size: size_t),
             (RtSigreturn = 15) => do_rt_sigreturn(context: *mut CpuContext),
             (Ioctl = 16) => do_ioctl(fd: FileDesc, cmd: u32, argp: *mut u8),