diff --git a/scrapyd/webservice.py b/scrapyd/webservice.py
index 1df2323e..4dd575fe 100644
--- a/scrapyd/webservice.py
+++ b/scrapyd/webservice.py
@@ -72,7 +72,7 @@ def render_POST(self, txrequest):
             prevstate = "pending"
         spiders = self.root.launcher.processes.values()
         for s in spiders:
-            if s.job == jobid:
+            if s.project == project and s.job == jobid:
                 s.transport.signalProcess(signal)
                 prevstate = "running"
         return {"node_name": self.root.nodename, "status": "ok", "prevstate": prevstate}