diff --git a/externs/shaka/net.js b/externs/shaka/net.js
index 58047b63d4..68540a5d00 100644
--- a/externs/shaka/net.js
+++ b/externs/shaka/net.js
@@ -60,7 +60,7 @@ shaka.extern.RetryParameters;
  *   retryParameters: !shaka.extern.RetryParameters,
  *   licenseRequestType: ?string,
  *   sessionId: ?string,
- *   streamDataCallback: ?function(BufferSource)
+ *   streamDataCallback: ?function(BufferSource):!Promise
  * }}
  *
  * @description
@@ -90,7 +90,7 @@ shaka.extern.RetryParameters;
  * @property {?string} sessionId
  *   If this is a LICENSE request, this field contains the session ID of the
  *   EME session that made the request.
- * @property {?function(BufferSource)} streamDataCallback
+ * @property {?function(BufferSource):!Promise} streamDataCallback
  *   A callback function to handle the chunked data of the ReadableStream.
  * @exportDoc
  */
diff --git a/lib/media/streaming_engine.js b/lib/media/streaming_engine.js
index 7b3ce91a61..d17c74fefa 100644
--- a/lib/media/streaming_engine.js
+++ b/lib/media/streaming_engine.js
@@ -1738,7 +1738,7 @@ shaka.media.StreamingEngine = class {
    * @param {!shaka.media.StreamingEngine.MediaState_} mediaState
    * @param {(!shaka.media.InitSegmentReference|!shaka.media.SegmentReference)}
    *   reference
-   * @param {?function(BufferSource)=} streamDataCallback
+   * @param {?function(BufferSource):!Promise=} streamDataCallback
    *
    * @return {!Promise.<BufferSource>}
    * @private
diff --git a/lib/net/http_fetch_plugin.js b/lib/net/http_fetch_plugin.js
index fbd086d017..454b4c2c5e 100644
--- a/lib/net/http_fetch_plugin.js
+++ b/lib/net/http_fetch_plugin.js
@@ -92,7 +92,7 @@ shaka.net.HttpFetchPlugin = class {
    * @param {!RequestInit} init
    * @param {shaka.net.HttpFetchPlugin.AbortStatus} abortStatus
    * @param {shaka.extern.ProgressUpdated} progressUpdated
-   * @param {?function(BufferSource)} streamDataCallback
+   * @param {?function(BufferSource):!Promise} streamDataCallback
    * @return {!Promise<!shaka.extern.Response>}
    * @private
    */
@@ -140,7 +140,7 @@ shaka.net.HttpFetchPlugin = class {
           if (!readObj.done) {
             loaded += readObj.value.byteLength;
             if (streamDataCallback) {
-              streamDataCallback(readObj.value);
+              await streamDataCallback(readObj.value);
             }
           }
 
diff --git a/lib/net/networking_engine.js b/lib/net/networking_engine.js
index 9da4a8ffb3..da5a5c23b8 100644
--- a/lib/net/networking_engine.js
+++ b/lib/net/networking_engine.js
@@ -196,7 +196,7 @@ shaka.net.NetworkingEngine = class extends shaka.util.FakeEventTarget {
    *
    * @param {!Array.<string>} uris
    * @param {shaka.extern.RetryParameters} retryParams
-   * @param {?function(BufferSource)=} streamDataCallback
+   * @param {?function(BufferSource):!Promise=} streamDataCallback
    * @return {shaka.extern.Request}
    * @export
    */
diff --git a/lib/util/networking.js b/lib/util/networking.js
index be189d945d..7f263bcd70 100644
--- a/lib/util/networking.js
+++ b/lib/util/networking.js
@@ -26,7 +26,7 @@ shaka.util.Networking = class {
    * @param {?number} start
    * @param {?number} end
    * @param {shaka.extern.RetryParameters} retryParameters
-   * @param {?function(BufferSource)=} streamDataCallback
+   * @param {?function(BufferSource):!Promise=} streamDataCallback
    * @return {shaka.extern.Request}
    */
   static createSegmentRequest(uris, start, end, retryParameters,