diff --git a/CHANGELOG.md b/CHANGELOG.md
index 80f9dd14..3cbf6622 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
+- SideloadedSubtitle
+  - Fixed a data race that could crash with `EXC_BAD_ACCESS` when playing a stream with side-loaded text tracks, caused by concurrent mutation of the internal request/subtitle collections from the playlist interception callbacks.
+
 ## [11.0.4] - 2026-05-29
 
 ### Changed
diff --git a/Code/Sideloaded-TextTracks/Sources/THEOplayerConnectorSideloadedSubtitle/AVSubtitlesLoader.swift b/Code/Sideloaded-TextTracks/Sources/THEOplayerConnectorSideloadedSubtitle/AVSubtitlesLoader.swift
index 6ae35533..92f09345 100644
--- a/Code/Sideloaded-TextTracks/Sources/THEOplayerConnectorSideloadedSubtitle/AVSubtitlesLoader.swift
+++ b/Code/Sideloaded-TextTracks/Sources/THEOplayerConnectorSideloadedSubtitle/AVSubtitlesLoader.swift
@@ -17,12 +17,23 @@ class AVSubtitlesLoader: NSObject {
     }
 
     private let _subtitles: [TextTrackDescription]
-    private var subtitles: [TextTrackDescription] = []
     private let transformer = SubtitlesTransformer()
     private let synchronizer: SubtitlesSynchronizer?
     private let _id: String
     private var variantTotalDuration: Double = 0
-    private var requestMap: [URL: URLRequest] = [:]
+
+    private let subtitlesLock = NSLock()
+    private var subtitlesStorage: [TextTrackDescription] = []
+    private var subtitles: [TextTrackDescription] {
+        get { self.subtitlesLock.lock(); defer { self.subtitlesLock.unlock() }; return self.subtitlesStorage }
+        set { self.subtitlesLock.lock(); defer { self.subtitlesLock.unlock() }; self.subtitlesStorage = newValue }
+    }
+    private let requestMapLock = NSLock()
+    private var requestMapStorage: [URL: URLRequest] = [:]
+    private var requestMap: [URL: URLRequest] {
+        get { self.requestMapLock.lock(); defer { self.requestMapLock.unlock() }; return self.requestMapStorage }
+        set { self.requestMapLock.lock(); defer { self.requestMapLock.unlock() }; self.requestMapStorage = newValue }
+    }
     
     init(subtitles: [TextTrackDescription], id: String, player: THEOplayer? = nil) {
         self._subtitles = subtitles