diff --git a/pes_to_spec/model.py b/pes_to_spec/model.py
index 389c0827bc759812fbdc28049f6301b37fc2dcd1..911ddd462b1a797475afb757d562334d7304fec2 100644
--- a/pes_to_spec/model.py
+++ b/pes_to_spec/model.py
@@ -337,13 +337,14 @@ class SelectRelevantLowResolution(TransformerMixin, BaseEstimator):
         """
         # reduce on channel and on train ID
         sum_low_res = - np.mean(sum(list(X.values())), axis=0)
+        zero_level = np.amin(sum_low_res)
         axis = np.arange(0.0, sum_low_res.shape[0], 1.0)
         #widths = np.arange(10, 50, step=5)
         #peak_idx = find_peaks_cwt(sum_low_res, widths)
         gaussian = np.exp(-0.5*(axis - sum_low_res.shape[0]//2)**2/20**2)
         gaussian /= np.sum(gaussian, axis=0, keepdims=True)
         # apply it to the data
-        smoothened = fftconvolve(sum_low_res, gaussian, mode="same", axes=0)
+        smoothened = fftconvolve(sum_low_res - zero_level, gaussian, mode="same", axes=0)
         peak_idx = [np.argmax(smoothened)]
         if len(peak_idx) < 1:
             raise PromptNotFoundError()