diff --git a/lib/media/drm_engine.js b/lib/media/drm_engine.js
index 25fa3f2dec..6ec5971e56 100644
--- a/lib/media/drm_engine.js
+++ b/lib/media/drm_engine.js
@@ -750,6 +750,17 @@ shaka.media.DrmEngine = class {
           return;
         }
       }
+      let duplicate = false;
+      this.storedPersistentSessions_.forEach((metadata, sessionId) => {
+        if (!duplicate &&
+            shaka.util.BufferUtils.equal(initData, metadata.initData)) {
+          duplicate = true;
+        }
+      });
+      if (duplicate) {
+        shaka.log.debug('Ignoring duplicate init data.');
+        return;
+      }
     }
 
     // If there are pre-existing sessions that have all been loaded
diff --git a/test/media/drm_engine_unit.js b/test/media/drm_engine_unit.js
index 9ea2ce18fc..31abc7b3a6 100644
--- a/test/media/drm_engine_unit.js
+++ b/test/media/drm_engine_unit.js
@@ -1286,20 +1286,7 @@ describe('DrmEngine', () => {
 
           await Util.shortDelay();
 
-          session3.on['message']({
-            target: session3,
-            message: new Uint8Array(0),
-            messageType: 'license-request'});
-
-          session3.keyStatuses.forEach.and.callFake((callback) => {
-            callback(keyId1, 'usable');
-          });
-
-          session3.on['keystatuseschange']({target: session3});
-
-          await Util.shortDelay();
-
-          expect(mockMediaKeys.createSession).toHaveBeenCalledTimes(3);
+          expect(mockMediaKeys.createSession).toHaveBeenCalledTimes(2);
           expect(mockMediaKeys.createSession)
               .toHaveBeenCalledWith('persistent-license');
           expect(session1.load)
@@ -1309,11 +1296,6 @@ describe('DrmEngine', () => {
               .toHaveBeenCalledWith('persistent-license');
           expect(session2.load)
               .toHaveBeenCalledWith('persistent-session-id-2');
-
-          expect(mockMediaKeys.createSession)
-              .toHaveBeenCalledWith('temporary');
-          expect(session3.generateRequest)
-              .toHaveBeenCalledWith('cenc', initData1);
         });
   });  // describe('attach')