diff --git a/src/tab_details.py b/src/tab_details.py
index cd96ecc4d..aae9f1f0d 100644
--- a/src/tab_details.py
+++ b/src/tab_details.py
@@ -93,7 +93,7 @@ class DetailsTabManager(object):
         if state != None:
             gc.set_foreground(colormap.alloc_color('#2020FF'))
             progress_window.draw_rectangle(gc, True, 0, top, int(size[0] * state['progress']), 4)
-            num_pieces = state["num_pieces"]
+            num_pieces = state["total_wanted"] / state["piece_length"]
             for pieces_range in state['pieces']:
                 range_first = pieces_range[0] * size[0] / num_pieces
                 range_length = ((pieces_range[1] - pieces_range[0] + 1) * size[0] / num_pieces)