diff --git a/src/pkg/syscall/syscall_unix.go b/src/pkg/syscall/syscall_unix.go
index cc1e4f7..26a12a6 100644
--- a/src/pkg/syscall/syscall_unix.go
+++ b/src/pkg/syscall/syscall_unix.go
@@ -111,3 +111,19 @@
 func (e Errno) Timeout() bool {
 	return e == EAGAIN || e == EWOULDBLOCK || e == ETIMEDOUT
 }
+
+// A Signal is a number describing a process signal.
+// It implements the os.Signal interface.
+type Signal int
+
+func (s Signal) Signal() {}
+
+func (s Signal) String() string {
+	if 0 <= s && int(s) < len(signals) {
+		str := signals[s]
+		if str != "" {
+			return str
+		}
+	}
+	return "signal " + itoa(int(s))
+}