diff --git a/src/calng/Gotthard2Correction.py b/src/calng/Gotthard2Correction.py
index 64578f92dea1a90b2a5663efa94eb2a18d7f54a8..d5ac772250bd69f3c9af7221f33fa1daf18abcd2 100644
--- a/src/calng/Gotthard2Correction.py
+++ b/src/calng/Gotthard2Correction.py
@@ -353,7 +353,7 @@ class Gotthard2Correction(BaseCorrection):
             replacement = self.unsafe_get("preview.replaceNanWith")
             streak_preview[np.isnan(streak_preview)] = replacement
             streak_preview[np.isinf(streak_preview)] = replacement
-            frame_sums = np.sum(streak_preview, axis=0)
+            frame_sums = np.sum(streak_preview, axis=1)
             self._write_preview_outputs(
                 (
                     ("preview.outputRaw", preview_raw),