diff --git a/source/_components/history_graph.markdown b/source/_components/history_graph.markdown
index a929385fa18..42a8fe79046 100644
--- a/source/_components/history_graph.markdown
+++ b/source/_components/history_graph.markdown
@@ -71,7 +71,6 @@ history_graph:
       - sensor.inside_temperature
     hours_to_show: 120
     # refresh: 0
-
 ```
 
-
+For sensors to automatically be combined into one graph they need to have exactly the same unit of measurement. This is important if you have, e.g., a unit-less temperature `state_topic` MQTT sensor and you want to combine this with a weather sensor. `unit_of_measurement:` of the MQTT sensor then needs to be set to `°C`.