diff --git a/large_image/tilesource/utilities.py b/large_image/tilesource/utilities.py
index 22a8ce78f..02d68dd10 100644
--- a/large_image/tilesource/utilities.py
+++ b/large_image/tilesource/utilities.py
@@ -999,7 +999,7 @@ def histogramThreshold(histogram, threshold, fromMax=False):
             break
         tally += hist[idx]
     if len(_recentThresholds) > 100:
-        _recentThresholds.empty()
+        _recentThresholds.clear()
     _recentThresholds[key] = result
     return result