diff --git a/lib/player.js b/lib/player.js
index 584a9e1944..3a628b1d07 100644
--- a/lib/player.js
+++ b/lib/player.js
@@ -5972,6 +5972,13 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       references.push(reference);
     }
 
+    let segmentMimeType = mimeType;
+    if (references.length) {
+      segmentMimeType = await shaka.net.NetworkingUtils.getMimeType(
+          references[0].getUris()[0],
+          this.networkingEngine_, this.config_.manifest.retryParameters);
+    }
+
     /** @type {shaka.extern.Stream} */
     const stream = {
       id: this.nextExternalStreamId_++,
@@ -5979,7 +5986,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       groupId: null,
       createSegmentIndex: () => Promise.resolve(),
       segmentIndex: new shaka.media.SegmentIndex(references),
-      mimeType: mimeType || '',
+      mimeType: segmentMimeType || '',
       codecs: '',
       kind: '',
       encrypted: false,
@@ -6003,7 +6010,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       external: true,
       fastSwitching: false,
       fullMimeTypes: new Set([shaka.util.MimeUtils.getFullType(
-          mimeType || '', '')]),
+          segmentMimeType || '', '')]),
     };
 
     if (this.loadMode_ == shaka.Player.LoadMode.SRC_EQUALS) {
diff --git a/test/player_integration.js b/test/player_integration.js
index b919baef81..6eba374cc6 100644
--- a/test/player_integration.js
+++ b/test/player_integration.js
@@ -1341,6 +1341,8 @@ describe('Player', () => {
 
           expect(player.getImageTracks()).toEqual([newTrack]);
 
+          expect(newTrack.mimeType).toBe('image/jpeg');
+
           const thumbnail1 = await player.getThumbnails(newTrack.id, 0);
           expect(thumbnail1.startTime).toBe(0);
           expect(thumbnail1.duration).toBe(5);
@@ -1379,6 +1381,8 @@ describe('Player', () => {
 
           expect(player.getImageTracks()).toEqual([newTrack]);
 
+          expect(newTrack.mimeType).toBe('image/jpeg');
+
           const thumbnail1 = await player.getThumbnails(newTrack.id, 0);
           expect(thumbnail1.startTime).toBe(0);
           expect(thumbnail1.duration).toBe(5);
diff --git a/test/player_src_equals_integration.js b/test/player_src_equals_integration.js
index be27d27cb1..76d0448ddd 100644
--- a/test/player_src_equals_integration.js
+++ b/test/player_src_equals_integration.js
@@ -453,6 +453,8 @@ describe('Player Src Equals', () => {
 
           expect(player.getImageTracks()).toEqual([newTrack]);
 
+          expect(newTrack.mimeType).toBe('image/jpeg');
+
           const thumbnail1 = await player.getThumbnails(newTrack.id, 0);
           expect(thumbnail1.startTime).toBe(0);
           expect(thumbnail1.duration).toBe(5);
@@ -491,6 +493,8 @@ describe('Player Src Equals', () => {
 
           expect(player.getImageTracks()).toEqual([newTrack]);
 
+          expect(newTrack.mimeType).toBe('image/jpeg');
+
           const thumbnail1 = await player.getThumbnails(newTrack.id, 0);
           expect(thumbnail1.startTime).toBe(0);
           expect(thumbnail1.duration).toBe(5);