diff --git a/level1c4pps/vgac2pps_lib.py b/level1c4pps/vgac2pps_lib.py
index 3168891..e26f439 100644
--- a/level1c4pps/vgac2pps_lib.py
+++ b/level1c4pps/vgac2pps_lib.py
@@ -427,7 +427,7 @@
         },
         "tb12_twilight": {
             "viirs_channel": "M16",
-            "slope": 0.9973,
+            "slope": 0.9967,
             "offset": -0.7479,
             "min_sunzenith": 80,
             "max_sunzenith": 90,