diff --git a/buffet/commands/dbus_command_proxy_unittest.cc b/buffet/commands/dbus_command_proxy_unittest.cc
index 94b4906..3cb907d 100644
--- a/buffet/commands/dbus_command_proxy_unittest.cc
+++ b/buffet/commands/dbus_command_proxy_unittest.cc
@@ -107,7 +107,7 @@
   }
 
   DBusCommandProxy* GetCommandProxy() const {
-    CHECK_EQ(command_instance_->proxies_.size(), 1);
+    CHECK_EQ(command_instance_->proxies_.size(), 1U);
     return static_cast<DBusCommandProxy*>(command_instance_->proxies_[0].get());
   }