This bug occurs in Ubuntu 20.10 when both guile-2.2-dev and guile-3.0-dev packages are installed. An autotools project reproducing the bug is included. In order to reproduce the bug give commands "autoreconf -ivf" and "./configure". I get the following output from configure: --- ... configure: checking for guile 2.2 configure: found guile 2.2 checking for guile-2.0.14... no checking for guile2.0.14... no checking for guile-2.0... no checking for guile2.0... no checking for guile-2... no checking for guile2... no checking for guile... /usr/bin/guile configure: error: found development files for Guile 2.2, but /usr/bin/guile has effective version 3.0 ---      - Tommi Höynälänmaa