diff --git a/docs/development_guidelines.md b/docs/development_guidelines.md
index c5b06948..1f9ba7e2 100644
--- a/docs/development_guidelines.md
+++ b/docs/development_guidelines.md
@@ -90,3 +90,9 @@ Prefer [new style string formatting](https://www.python.org/dev/peps/pep-3101/)
 "{} {}".format('New', 'style')
 "%s %s" % ('Old', 'style')
 ```
+
+Except when doing logging here the format is:
+
+```python
+_LOGGER.info("Can't connect to the webservice %s at %s", string1, string2)
+```