diff --git a/gazebo/gui/TimePanel.cc b/gazebo/gui/TimePanel.cc
--- a/gazebo/gui/TimePanel.cc
+++ b/gazebo/gui/TimePanel.cc
@@ -178,7 +178,7 @@
 }
 
 /////////////////////////////////////////////////
-void TimePanel::OnFullScreen(bool & /*_value*/)
+void TimePanel::OnFullScreen(bool /*_value*/)
 {
   /*if (_value)
     this->hide();
diff --git a/gazebo/gui/TimePanel.hh b/gazebo/gui/TimePanel.hh
--- a/gazebo/gui/TimePanel.hh
+++ b/gazebo/gui/TimePanel.hh
@@ -66,7 +66,7 @@
       /// \brief Called when the GUI enters/leaves full-screen mode.
       /// \param[in] _value True when entering full screen, false when
       /// leaving.
-      private: void OnFullScreen(bool &_value);
+      private: void OnFullScreen(bool _value);
 
       /// \brief Called when a world stats message is received.
       /// \param[in] _msg World statistics message.