Problem when define Line Style and Linewidth

I am using the below code to plot 3 lines and when I define the Line Style and Linewidth, the text in the legend disappears. I tried rescaling the figure by using 'Position' and make it bigger but this didn'r solve the problem. Do you know how can I fix this? I am using the 2017b version.

 t = linspace(0,5,100);
 x = t.^2;
 y = t.^3;
 z = t.^4;

 figure;
 plot(t,x,'Linewidth',1)
 hold on
 plot(t,y,'--','Linewidth',1)
 plot(t,z,':','Linewidth',1)
 legend({'x','y','z'},'Location','Northwest')

[Star Strider]

With the code you posted, I cannot reproduce the problem you describe. Your code runs correctly for me, and the legend box, text, and correct line types and color designations appear (in R2017b).