A problem in using imhist to display histogram of indexed image

First i convert the image to an indexed image, and use only 5 colors to show what is my problem.

clear
img = imread('peppers.png');
[x,map] = rgb2ind(img,5);

figure;
imhist(x,map)

the colorbar doesn't match with the histogarm bars, this is my colormap:

 map =

    0.2784    0.1373    0.2353
    0.7608    0.1686    0.1373
    0.8902    0.7255    0.6353
    0.4275    0.3765    0.2235
    0.8471    0.5569    0.1020

the first one isn't white, It seems that the colorbar is shifted by one.