When launching gazebo no GUI overlay apears, and 'undefined symbol' error is printed in terminal

Hi. I followed GUI overlay tutorial "Display Simulation Time". When launching Gazebo no GUI overlay appears, and following error is printed in the terminal: [Err] [Plugin.hh:180] Failed to load plugin /.../ libgui_example_time_widget.so: undefined symbol: _ZN5QTest18lastMouseTimestampE [Err] [RenderWidget.cc:311] Unable to create gui overlay plugin with filename[libgui_example_time_widget.so] The other tutorial "Spawn spheres" results in similar error I am using Gazebo 9.0.0 Ubuntu 18.04 LTS Qt version 5.9.5