diff --git a/pypeit/core/gui/identify.py b/pypeit/core/gui/identify.py
index 8902f1b093..687e566689 100644
--- a/pypeit/core/gui/identify.py
+++ b/pypeit/core/gui/identify.py
@@ -247,6 +247,8 @@ def initialise(cls, arccen, lamps, slits, slit=0, par=None, wv_calib_all=None,
 
         if sigdetect is None:
             sigdetect = par['sigdetect']
+            if isinstance(sigdetect, list):
+                sigdetect = sigdetect[slit]
         print(f"Using {sigdetect} for sigma detection")
 
         # If a wavelength calibration has been performed already, load it:
@@ -264,6 +266,7 @@ def initialise(cls, arccen, lamps, slits, slit=0, par=None, wv_calib_all=None,
             msgs.warn("No wavelength calibration supplied!")
             msgs.info("No wavelength solution will be loaded.")
             wv_calib = None
+
         # Extract the lines that are detected in arccen
         thisarc = arccen[:, slit]
         if nonlinear_counts is None: