perf report addr2line: /proc/kcore: File format not recognized

Hello,
I'm on ubuntu bionic, binutils is 2.30, perf version 4.15.18

I'm using
sudo perf record -g -c 100000 -e cycles:u,instructions:u ./executable

to sample cycles and instructions.

However I cannot see source code line numbers with perf report

as seen here:
sudo perf report --stdio --show-nr-samples --percent-limit 4 --sort=srcline
[sudo] password for harubyy:
addr2line: /proc/kcore: File format not recognized
addr2line has no output for /proc/kcore
addr2line: /proc/kcore: File format not recognized
addr2line has no output for /proc/kcore
addr2line: /proc/kcore: File format not recognized
addr2line has no output for /proc/kcore
addr2line: /proc/kcore: File format not recognized
addr2line has no output for /proc/kcore
addr2line: /proc/kcore: File format not recognized
addr2line has no output for /proc/kcore

I hope someone can help me with this.
Thanks