Focal Lenght not reading properly when zooming???

[chatopedro]

When using a Canon Lens 18-135 f5-5.6 (lens kit that came with my 60d) I realized the focal lenght stays always in 44m regardless to the zooming.

However when I use a Canon 50mm f1.4 it the focal lenght shown in ML is 50mm.

Is there anything wrong when using the zoom lens???Should the focal lenght vary while zooming?