diff --git a/demo/theme.html b/demo/theme.html
index e951c84c36..22b59b7fdc 100644
--- a/demo/theme.html
+++ b/demo/theme.html
@@ -12,6 +12,7 @@
 <link rel="stylesheet" href="../theme/base16-light.css">
 <link rel="stylesheet" href="../theme/blackboard.css">
 <link rel="stylesheet" href="../theme/cobalt.css">
+<link rel="stylesheet" href="../theme/colorforth.css">
 <link rel="stylesheet" href="../theme/eclipse.css">
 <link rel="stylesheet" href="../theme/elegant.css">
 <link rel="stylesheet" href="../theme/erlang-dark.css">
@@ -81,6 +82,7 @@ <h2>Theme Demo</h2>
     <option>base16-light</option>
     <option>blackboard</option>
     <option>cobalt</option>
+    <option>colorforth</option>
     <option>eclipse</option>
     <option>elegant</option>
     <option>erlang-dark</option>
diff --git a/theme/colorforth.css b/theme/colorforth.css
index a54e45a91e..73fbf80824 100644
--- a/theme/colorforth.css
+++ b/theme/colorforth.css
@@ -29,3 +29,5 @@
 .cm-s-colorforth .CodeMirror-selected { background: #333d53 !important; }
 
 .cm-s-colorforth span.cm-compilation { background: rgba(255, 255, 255, 0.12); }
+
+.cm-s-colorforth .CodeMirror-activeline-background {background: #253540 !important;}