diff --git a/test/sys/test_signal.rs b/test/sys/test_signal.rs
index bf607497be..7494b71234 100644
--- a/test/sys/test_signal.rs
+++ b/test/sys/test_signal.rs
@@ -283,6 +283,7 @@ fn test_from_and_into_iterator() {
 #[test]
 #[cfg(not(target_os = "redox"))]
 fn test_sigaction() {
+    let _m = crate::SIGNAL_MTX.lock();
     thread::spawn(|| {
         extern "C" fn test_sigaction_handler(_: libc::c_int) {}
         extern "C" fn test_sigaction_action(