diff --git a/src/fontra/client/css/tooltip.css b/src/fontra/client/css/tooltip.css
index 0255f07b6..eb927ad55 100644
--- a/src/fontra/client/css/tooltip.css
+++ b/src/fontra/client/css/tooltip.css
@@ -30,7 +30,7 @@
   left: 50%;
   width: 0;
   height: 0;
-  bottom: calc(100%);
+  bottom: 100%;
   margin-left: -2px;
   border: 1px solid black;
   border-color: #272727 transparent transparent transparent;