diff --git a/lib/text/ttml_text_parser.js b/lib/text/ttml_text_parser.js
index 7bb70fe92c..ac07d6cfd8 100644
--- a/lib/text/ttml_text_parser.js
+++ b/lib/text/ttml_text_parser.js
@@ -574,8 +574,28 @@ shaka.text.TtmlTextParser = class {
 
     const fontFamily = TtmlTextParser.getStyleAttribute_(
         cueElement, region, styles, 'fontFamily', shouldInheritRegionStyles);
+    // See https://github.com/sandflow/imscJS/blob/1.1.3/src/main/js/html.js#L1384
     if (fontFamily) {
-      cue.fontFamily = fontFamily;
+      switch (fontFamily) {
+        case 'monospaceSerif':
+          cue.fontFamily = 'Courier New,Liberation Mono,Courier,monospace';
+          break;
+        case 'proportionalSansSerif':
+          cue.fontFamily = 'Arial,Helvetica,Liberation Sans,sans-serif';
+          break;
+        case 'sansSerif':
+          cue.fontFamily = 'sans-serif';
+          break;
+        case 'monospaceSansSerif':
+          cue.fontFamily = 'Consolas,monospace';
+          break;
+        case 'proportionalSerif':
+          cue.fontFamily = 'serif';
+          break;
+        default:
+          cue.fontFamily = fontFamily;
+          break;
+      }
     }
 
     const fontWeight = TtmlTextParser.getStyleAttribute_(