diff --git a/mrcnn/config.py b/mrcnn/config.py
index ae5cb1d9dc19bd0bf70ab359de37134ededda277..a7fdd1b5ea93acd0835f9ffef5f20c1c453276f9 100644
--- a/mrcnn/config.py
+++ b/mrcnn/config.py
@@ -90,6 +90,9 @@ class Config(object):
 
     # How many anchors per image to use for RPN training
     RPN_TRAIN_ANCHORS_PER_IMAGE = 256
+    
+    # ROIs kept after tf.nn.top_k and before non-maximum suppression
+    PRE_NMS_LIMIT = 6000
 
     # ROIs kept after non-maximum suppression (training and inference)
     POST_NMS_ROIS_TRAINING = 2000