def merge_hist(hist1, hist2):
    """
    Merge two hist-dicts.

    Args:
        hist1 (dict): Hist dict from fit.
        hist2 (dict): Hist dict from fit.

    Returns:
        outhist (dict): hist1 + hist2.

    """
    outhist = {}
    for x, y in hist1.items():
        outhist.update({x: hist1[x] + hist2[x]})
    return outhist