diff --git a/pims/pyav_reader.py b/pims/pyav_reader.py
index 2b453ee..40caa1e 100644
--- a/pims/pyav_reader.py
+++ b/pims/pyav_reader.py
@@ -2,6 +2,7 @@
                         unicode_literals)
 
 import numpy as np
+import threading
 
 from pims.base_frames import FramesSequence
 from pims.frame import Frame
@@ -27,6 +28,28 @@ def _next_video_packet(container_iter):
     raise ValueError("Could not find any video packets.")
 
 
+class threadsafe_iter:
+    """Takes an iterator/generator and makes it thread-safe by
+    serializing call to the `next` method of given iterator/generator.
+    """
+    def __init__(self, it):
+        self.it = it
+        self.lock = threading.Lock()
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        with self.lock:
+            return next(self.it)
+          
+def threadsafe_generator(f):
+    """A decorator that takes a generator function and makes it thread-safe.
+    """
+    def g(*a, **kw):
+        return threadsafe_iter(f(*a, **kw))
+    return g
+          
 class WrapPyAvFrame(object):
     def __init__(self, frame, frame_no, metadata=None):
         self.frame_no = frame_no
@@ -46,7 +69,7 @@ def to_frame(self):
                              frame_no=self.frame_no, metadata=self.metadata)
         return self.arr
 
-
+@threadsafe_generator
 def _gen_frames(demuxer, time_base, frame_rate=1., first_pts=0):
     for packet in demuxer:
         for frame in packet.decode():