diff --git a/oslo_messaging/tests/functional/zmq/multiproc_utils.py b/oslo_messaging/tests/functional/zmq/multiproc_utils.py
index fb66615b6..be6f1c422 100644
--- a/oslo_messaging/tests/functional/zmq/multiproc_utils.py
+++ b/oslo_messaging/tests/functional/zmq/multiproc_utils.py
@@ -141,7 +141,7 @@ class Server(object):
                                                      self.log_queue,
                                                      self.ready))
         self.process.start()
-        LOG.debug("Server process started: pid: %d" % self.process.pid)
+        LOG.debug("Server process started: pid: %d", self.process.pid)
 
     def _run_server(self, conf, url, log_queue, ready):
         server_configurer(log_queue)
@@ -161,8 +161,8 @@ class Server(object):
             LOG.debug("Waiting for the stop signal ...")
             time.sleep(1)
         self.rpc_server.stop()
-        LOG.debug("Leaving process T:%s Pid:%d" % (str(target),
-                                                   os.getpid()))
+        LOG.debug("Leaving process T:%s Pid:%d", (str(target),
+                                                  os.getpid()))
 
     def cleanup(self):
         LOG.debug("Stopping server")
@@ -217,7 +217,7 @@ class MutliprocTestCase(utils.SkipIfNoTransportURL):
 
     def spawn_server(self, name, wait_for_server=False, topic=None):
         srv = Server(self.conf, self.log_queue, self.url, name, topic)
-        LOG.debug("[SPAWN] %s (starting)..." % srv.name)
+        LOG.debug("[SPAWN] %s (starting)...", srv.name)
         srv.start()
         if wait_for_server:
             while not srv.ready.value:
diff --git a/tools/simulator.py b/tools/simulator.py
index 47d5b9184..e77a75c78 100755
--- a/tools/simulator.py
+++ b/tools/simulator.py
@@ -446,7 +446,7 @@ def main():
         with open('./oslo_res_%s.txt' % args.server, 'a+') as f:
             f.write(log_msg + '\n')
 
-        LOG.info("calls finished, wait %d seconds" % args.exit_wait)
+        LOG.info("calls finished, wait %d seconds", args.exit_wait)
         time.sleep(args.exit_wait)