diff --git a/lib/player.js b/lib/player.js
index 4899b81175..8be4517d09 100644
--- a/lib/player.js
+++ b/lib/player.js
@@ -1440,11 +1440,13 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
         // "preload" here without prefetch.
         // That way, both a preload and normal load can follow the same code
         // paths.
+        // NOTE: await preloadInner_ can be outside the mutex because it should
+        // not mutate "this".
         preloadManager = await this.preloadInner_(
             assetUri, startTime, mimeType, /* standardLoad= */ true);
         if (preloadManager) {
           preloadManager.setEventHandoffTarget(this);
-          await preloadManager.start();
+          await mutexWrapOperation(() => preloadManager.start(), 'preload');
         }
       } else {
         // Hook up events, so any events emitted by the preloadManager will
diff --git a/test/player_load_graph_integration.js b/test/player_load_graph_integration.js
index 27be9657dc..b8c18208d4 100644
--- a/test/player_load_graph_integration.js
+++ b/test/player_load_graph_integration.js
@@ -756,6 +756,7 @@ describe('Player Load Graph', () => {
         'manifest-parser',
         'manifest',
         'drm-engine',
+        // Excludes 'unload'.
       ]);
 
       /** @type {!Set.<string>} */
@@ -774,6 +775,7 @@ describe('Player Load Graph', () => {
         await player.attach(video);
         player.load('test:sintel').catch(() => {});
       } else {
+        goog.asserts.assert(state == 'unload', 'Unrecognized testing state!');
         await player.attach(video);
         await player.load('test:sintel');
         player.unload().catch(() => {});