diff --git a/mmtwfs/wfs.py b/mmtwfs/wfs.py
index 0290e31..344cfe7 100644
--- a/mmtwfs/wfs.py
+++ b/mmtwfs/wfs.py
@@ -1027,6 +1027,7 @@ def vlt_seeing(self, spot, mode, airmass=None):
         with warnings.catch_warnings():
             # ignore astropy warnings about issues with the fitting process...
             warnings.simplefilter("ignore")
+            isolist = []
             # the initial angle seems to matter for getting successful fits so try a set
             for ang in [0, 45, 90, 135, 180]:
                 try: