How to define custom TraceListener in app.config

I have implemented a custom trace listener (derived from TextWriteTraceListener) and now I would like to set my application to use it instead of standard TextWriteTraceListener.

First I added default TextWriteTraceListener in order to make sure it works ok and it does. Here's my app.config:

<configuration>
    <system.diagnostics>
        <trace autoflush="true" indentsize="4">
            <listeners>
                <add name="TextListener"  type="System.Diagnostics.TextWriterTraceListener" initializeData="trace.log" />
            <remove name="Default" />
            </listeners>
        </trace>
    </system.diagnostics>
</configuration>

Now my trace listener is defined in MyApp.Utils namespace and it's called FormattedTextWriterTraceListener. So I changed the type in the config above to MyApp.Utils.FormattedTextWriterTraceListener and it currently looks like that:

<configuration>
    <system.diagnostics>
        <trace autoflush="true" indentsize="4">
            <listeners>
                <add name="MyTextListener" type="MyApp.Utils.FormattedTextWriterTraceListener" initializeData="trace.log" />
            <remove name="Default" />
            </listeners>
        </trace>
    </system.diagnostics>
</configuration>

However now when I try to log something I'm getting a ConfigurationErrorsException with the message:

Couldn't find type for class MyApp.Utils.FormattedTextWriterTraceListener.

Does anyone knows how can I set up this custom listener in config and if it's even possible?

Try specifying an assembly too, like so:

<configuration>
    <system.diagnostics>
        <trace autoflush="true" indentsize="4">
            <listeners>
                <add name="TextListener" 
                    type="MyApp.Utils.FormattedTextWriterTraceListener, MyApp"
                    initializeData="trace.log" />
            <remove name="Default" />
            </listeners>
        </trace>
    </system.diagnostics>
</configuration>