diff --git a/snippets/pretty-text-underline.md b/snippets/pretty-text-underline.md
index 3f3012ce5..e1a45c062 100644
--- a/snippets/pretty-text-underline.md
+++ b/snippets/pretty-text-underline.md
@@ -24,6 +24,10 @@ Natively implemented as `text-decoration-skip-ink: auto` but it has less control
   background-repeat: repeat-x;
   background-size: 1px 1px;
 }
+.pretty-text-underline::-moz-selection {
+  background-color: rgba(0, 150, 255, 0.3);
+  text-shadow: none;
+}
 .pretty-text-underline::selection {
   background-color: rgba(0, 150, 255, 0.3);
   text-shadow: none;
@@ -50,6 +54,11 @@ Natively implemented as `text-decoration-skip-ink: auto` but it has less control
   background-size: 1px 1px;
 }
 
+.snippet-demo__pretty-text-underline::-moz-selection {
+  background-color: rgba(0, 150, 255, 0.3);
+  text-shadow: none;
+}
+
 .snippet-demo__pretty-text-underline::selection {
   background-color: rgba(0, 150, 255, 0.3);
   text-shadow: none;
@@ -69,7 +78,7 @@ Natively implemented as `text-decoration-skip-ink: auto` but it has less control
 
 #### Browser support
 
-<span class="snippet__support-note">✅ No caveats.</span>
+<span class="snippet__support-note">⚠️ Firefox requires a vendor prefix for the selection pseudo-selector to work.</span>
 
 * https://caniuse.com/#feat=css-textshadow
 * https://caniuse.com/#feat=css-gradients