diff --git a/framework/core/less/forum/Post.less b/framework/core/less/forum/Post.less
index 3f3761bd7..93bba10d8 100644
--- a/framework/core/less/forum/Post.less
+++ b/framework/core/less/forum/Post.less
@@ -147,6 +147,9 @@
       border-radius: 0;
       display: block;
       overflow-x: auto;
+      // Backwards compatibility for browsers that don't support `max()`
+      max-height: 50vh;
+      max-height: ~"max(50vh, 250px)";
     }
   }
   h1, h2, h3, h4, h5, h6 {