diff --git a/imagery/i.atcorr/create_iwave.py b/imagery/i.atcorr/create_iwave.py
index 75bcb1578d0..827b8be54c4 100644
--- a/imagery/i.atcorr/create_iwave.py
+++ b/imagery/i.atcorr/create_iwave.py
@@ -220,7 +220,7 @@ def get_max_wavelength(c, rthresh, fi):
         :param fi: filter function
         """
         while c < len(fi) - 1 and fi[c + 1] > rthresh:
-            c = c + 1
+            c += 1
         return np.floor(li[0] * 1000 + (2.5 * c))
 
     # keep in sync with IWave::parse()