max_cliques output file format messes vertex numbers

I have a graph of 3316864 vertices and 15314269 edges. Using max_cliques with an output file I found that vertex numbers which are greater than 1e6 are represented in a scientific notation with 5 decimal places so the last digit is lost. How can this be avoided?

Can you please show a complete reproducible example? I looked into the C code of the corresponding function, and it uses the %d format specifier. I do not see how it could result in scientific notation.