diff --git a/private/system_server.te b/private/system_server.te
index 4778daa..89a185d 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -110,6 +110,8 @@
 
 # Kill apps.
 allow system_server appdomain:process { getpgid sigkill signal };
+# signull allowed for kill(pid, 0) existence test.
+allow system_server appdomain:process { signull };
 
 # Set scheduling info for apps.
 allow system_server appdomain:process { getsched setsched };