diff --git a/src/pb_stub.cc b/src/pb_stub.cc
index f838fba8..e5e60ee5 100644
--- a/src/pb_stub.cc
+++ b/src/pb_stub.cc
@@ -1917,7 +1917,7 @@ ParentProcessActive(DWORD parent_id)
 bool
 ParentProcessActive(pid_t parent_id)
 {
-  return (kill(parent_id, 0) == -1);
+  return (kill(parent_id, 0) == 0);
 }
 #endif