diff --git a/config/nimalyzer.cfg b/config/nimalyzer.cfg
index 84bf799..d37583e 100644
--- a/config/nimalyzer.cfg
+++ b/config/nimalyzer.cfg
@@ -105,6 +105,17 @@ source tools/gendoc.nim
 source tools/genrule.nim
 source tests/utils/helpers.nim
 
+# Extensions
+# ----------
+# By default, the program adds to check only files with extensions *.nim* or
+# *.nims*. If your source code files have different extensions, you can add their
+# list with 'extensions' setting. All extensions must be separated by comma and
+# space. It is recommended to set this setting before any 'directory' settings.
+# The setting below will add extensions *.inc* and *.cfg* to the list of files'
+# extensions for 'directory' setting.
+# ::
+# extensions .inc, .cfg
+
 # Directory
 # ---------
 # The directory which content will be analyzed. The path must be in Unix form.