diff --git a/source/_components/sma.markdown b/source/_components/sma.markdown
index 8adc638dc77..4b440b9f8f4 100644
--- a/source/_components/sma.markdown
+++ b/source/_components/sma.markdown
@@ -133,7 +133,7 @@ Example:
 ```yaml
    custom:
       yesterday_consumption:
-         key: 6400_00543A01
+         key: '6400_00543A01'
          unit: kWh
          factor: 1000
 ```