diff --git a/lib/player.js b/lib/player.js
index 4969daaa75..50740826a5 100644
--- a/lib/player.js
+++ b/lib/player.js
@@ -4051,12 +4051,12 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       for (const keySystem in config['drm']['advanced']) {
         const {videoRobustness, audioRobustness} =
             config['drm']['advanced'][keySystem];
-        if ('videoRobustness' in keySystem &&
+        if ('videoRobustness' in config['drm']['advanced'][keySystem] &&
             !Array.isArray(keySystem['videoRobustness'])) {
           keySystem['videoRobustness'] = [videoRobustness];
           fixedUp = true;
         }
-        if ('audioRobustness' in keySystem &&
+        if ('audioRobustness' in config['drm']['advanced'][keySystem] &&
             !Array.isArray(keySystem['audioRobustness'])) {
           keySystem['audioRobustness'] = [audioRobustness];
           fixedUp = true;