diff --git a/nifty/operators/fft_operator/transformations/lm_transformation_helper.py b/nifty/operators/fft_operator/transformations/lm_transformation_helper.py
index 71041206553b39a32967ad0d8d19b35ecb97ee58..09fd0f7a33e84a57f8485ae1576bcdcf2972be45 100644
--- a/nifty/operators/fft_operator/transformations/lm_transformation_helper.py
+++ b/nifty/operators/fft_operator/transformations/lm_transformation_helper.py
@@ -17,8 +17,6 @@ def buildIdx(nr, lmax):
         new_dtype = np.float32
     elif nr.dtype == np.dtype('complex128'):
         new_dtype = np.float64
-    elif nr.dtype == np.dtype('complex256'):
-        new_dtype = np.float128
     else:
         raise TypeError("dtype of nr not supported.")