diff --git a/mopidy/scanner.py b/mopidy/scanner.py
index 695cda27..c3eda9ae 100644
--- a/mopidy/scanner.py
+++ b/mopidy/scanner.py
@@ -96,7 +96,7 @@ class Scanner(object):
         self.next_uri()
 
     def get_duration(self):
-        self.pipe.get_state()
+        self.pipe.get_state() # Block untill state change is done.
         try:
             return self.pipe.query_duration(
                 gst.FORMAT_TIME, None)[0] // gst.MSECOND