diff --git a/libcore/parser/SWFMovieDefinition.cpp b/libcore/parser/SWFMovieDefinition.cpp
index c0d8976..b8dbbf2 100644
--- a/libcore/parser/SWFMovieDefinition.cpp
+++ b/libcore/parser/SWFMovieDefinition.cpp
@@ -72,7 +72,8 @@ namespace gnash
 {
 
 SWFMovieLoader::SWFMovieLoader(SWFMovieDefinition& md)
-    : _movie_def(md)
+    : _movie_def(md),
+      _canceled(false)
 {
 }
 
@@ -123,6 +124,20 @@ SWFMovieLoader::start()
     return true;
 }
 
+void
+SWFMovieLoader::cancel()
+{
+    std::lock_guard<std::mutex> lock(_mutex);
+    _canceled = true;
+}
+
+bool
+SWFMovieLoader::cancelled() const
+{
+    std::lock_guard<std::mutex> lock(_mutex);
+    return _canceled;
+}
+
 
 //
 // SWFMovieDefinition
@@ -150,7 +165,7 @@ SWFMovieDefinition::SWFMovieDefinition(const RunResources& runResources)
 SWFMovieDefinition::~SWFMovieDefinition()
 {
     // Request cancellation of the loading thread
-    _loadingCanceled = true;
+    _loader.cancel();
 }
 
 void
@@ -365,6 +380,8 @@ SWFMovieDefinition::ensure_frame_loaded(size_t framenum) const
 
     _waiting_for_frame = framenum;
 
+    assert(_loader.started());
+
     std::mutex m;
     std::unique_lock<std::mutex> lock(m);
 
@@ -373,7 +390,7 @@ SWFMovieDefinition::ensure_frame_loaded(size_t framenum) const
     // Make sure we don't wait here if the frame has been loaded, or the
     // loading thread has finished.
     _frame_reached_condition.wait(lock, [&] () {
-            return framenum <= _frames_loaded.load() || _loadingCanceled;
+            return framenum <= _frames_loaded.load() || _loader.cancelled();
         });
 
     return ( framenum <= _frames_loaded.load() );
@@ -454,7 +471,7 @@ SWFMovieDefinition::read_all_swf()
     try {
         while (left) {
 
-            if (_loadingCanceled.load()) {
+            if (_loader.cancelled()) {
                 log_debug("Loading thread cancellation requested, "
                         "returning from read_all_swf");
                 return;
@@ -499,7 +516,7 @@ SWFMovieDefinition::read_all_swf()
         _frames_loaded = m_frame_count;
         // Notify any thread waiting on frame reached condition
     }
-    _loadingCanceled = true;
+    _loader.cancel();
     _frame_reached_condition.notify_all();
 }
 
diff --git a/libcore/parser/SWFMovieDefinition.h b/libcore/parser/SWFMovieDefinition.h
index fc9a3b2..e0d43cc 100644
--- a/libcore/parser/SWFMovieDefinition.h
+++ b/libcore/parser/SWFMovieDefinition.h
@@ -88,12 +88,17 @@ public:
     /// Return true if called from the loader thread.
     bool isSelfThread() const;
 
+    void cancel();
+
+    bool cancelled() const;
+
 private:
 
     SWFMovieDefinition& _movie_def;
 
     mutable std::mutex _mutex;
     std::thread _thread;
+    bool _canceled;
 };
 
 /// The Characters dictionary associated with each SWF file.