diff --git a/ETA.py b/ETA.py
index 7741b15..885a91e 100755
--- a/ETA.py
+++ b/ETA.py
@@ -607,6 +607,14 @@ bias = {
 
 mean_bias = np.mean( [ bias[ 'top' ] , bias[ 'down' ] ] , axis = 0 )
 
+data[
+                           :                       ,
+    border[ 'x' ][ 'min' ] : border[ 'x' ][ 'max' ]
+] = data[
+                           :                       ,
+    border[ 'x' ][ 'min' ] : border[ 'x' ][ 'max' ]
+] - mean_bias
+
 if verbose:
     print( 'bias substraction finished' )
     print( 'starting to flatten the ETA' )
@@ -619,7 +627,7 @@ list_ = np.convolve(
                 border[ 'x' ][ 'min' ] : border[ 'x' ][ 'max' ]
             ]       ,
             axis = 1,
-        ) - mean_bias,
+        ),
     )            ,
     np.ones( 50 ),
     'same'       ,