diff --git a/docs/dynmetrics/index.html b/docs/dynmetrics/index.html
index c761a2c59..dfcad2204 100644
--- a/docs/dynmetrics/index.html
+++ b/docs/dynmetrics/index.html
@@ -44,7 +44,7 @@ endfor
     <formula>
       leading = <const>l</const> × fontSize
     </formula>
-    <formula>
+    <formula title="Base of natural logarithm">
       <const>e</const> ≈ <num>2.718</num>
     </formula>
   </p>