diff --git a/docs/units.rst b/docs/units.rst
index 198f04c..d50f361 100644
--- a/docs/units.rst
+++ b/docs/units.rst
@@ -11,4 +11,4 @@ Here are some examples, which `lives here <https://github.com/andymeneely/squib/
 
 .. raw:: html
 
-  <img src="units/units_00_expected.png">
+  <img src="units/units_00_expected.png" class="figure">