diff --git a/src/toolbox_scs/routines/boz.py b/src/toolbox_scs/routines/boz.py
index 61c1fbd13fd18fa6e0fd29da0a73cb63c8196f26..b8274bdbccc4884aa16eff252b698ab27ad76141 100644
--- a/src/toolbox_scs/routines/boz.py
+++ b/src/toolbox_scs/routines/boz.py
@@ -346,9 +346,9 @@ def find_rois(data_mean, threshold):
     rois: dictionnary of rois
     """
     # compute vertical and horizontal projection
-    pX = data_mean.sum(axis=0)
+    pX = data_mean.mean(axis=0)
     pX = pX[:256]  # half the ladder since there is a gap in the middle
-    pY = data_mean.sum(axis=1)
+    pY = data_mean.mean(axis=1)
 
     # along X
     lowX = int(np.argmax(pX[:64] > threshold))  # 1st occurrence returned