Twoside documentclass: Underfull \vbox (badness 10000) has occurred while \output is active

I'm using the documentclass article with the option twoside in order to customize the header and the footer for even and odd pages with the fancyhdr package. The compilation works, but the problem is that the output panel gives me the following badbox:

Underfull \vbox (badness 10000) has occurred while \output is active


I think the problem is due to the use of the geometry package, but I don't know how to solve it. What does it mean and how can I get rid of it? This is my preamble:

\documentclass[10pt,twoside]{article}
\usepackage[papersize={120mm,195mm},top=2.7cm,bottom=2.7cm,right=1.3cm,left=1.3cm]{geometry}%left1.6
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[polutonikogreek,italian,english]{babel}
\usepackage[italian]{varioref}
\usepackage{fancyhdr}

\pagestyle{fancy}
\fancyhf{}

• you have not provided a usable example, so it is hard to help, but perhaps add heightrounded to the geometry options – David Carlisle Feb 28 at 0:15
You need to make sure that the page size allows a full page of lines of text (which has no vertical flexibility) fit into \textheight The heightrounded option tells geometry to ensure this constraint is met.