Material Table Overwrite Toolbar Component

Question

To override a button in the Toolbar component of react Material Table, I copied the official Material Table Toolbar component and pasted it unchanged into my project. Then I overwrote the Toolbar component as described in the documentation:

<MaterialTable 
          title={"Test"}
          columns={this.state.columns} 
          data={this.state.data}
          components={
            {Toolbar:props => (
            <div>
                <MTableToolbar {...props}/>
            </div>)}
          }
          icons={tableIcons}
          options=
          {{
              showEmptyDataSourceMessage: true, 
              maxBodyHeight: 500
          }} />

But now I always get the following error: "Cannot read properties of undefined (reading 'root')". I went through the code and found that the prop classes seems to be undefined. At another place in my project I did almost exactly the same (i.e. in Material Table I overwrote the Toolbar component etc.) and it doesn't throw me the said error. Do any of you have any idea where the error might be coming from. Thanks in advance!