diff --git a/lib/xmet/sounding.py b/lib/xmet/sounding.py
index 8d4a078..64642a2 100644
--- a/lib/xmet/sounding.py
+++ b/lib/xmet/sounding.py
@@ -1,7 +1,7 @@
 import datetime
 import shapely
 
-from typing import Self
+from typing import Self, Optional
 
 from xmet.db     import Database, DatabaseTable, DatabaseOrder
 from xmet.coord  import COORD_SYSTEM
@@ -97,7 +97,7 @@ class Sounding(DatabaseTable):
     @staticmethod
     def valid_by_station(db: Database,
                          station: str,
-                         timestamp: datetime.datetime=None):
+                         timestamp: Optional[datetime.datetime]=None):
         sql = """
             select
                 id, station, timestamp_observed, timestamp_released,
@@ -215,10 +215,10 @@ class SoundingParams():
         self.cape = None
 
     @staticmethod
-    def cape(temp_line: Series,
-             moist_adiabat: Series,
-             lfc: tuple[float],
-             el: tuple[float]) -> float:
+    def find_cape(temp_line: Series,
+                  moist_adiabat: Series,
+                  lfc: tuple[float, float],
+                  el: tuple[float, float]) -> float:
         cape = 0.0
 
         p_lfc, p_el = lfc[1], el[1]
@@ -275,10 +275,10 @@ class SoundingParams():
         self.lcl  = lcl
         self.lfc  = lfc
         self.el   = el
-        self.cape = SoundingParams.cape(virtual_temp_line,
-                                        moist_adiabat,
-                                        lfc,
-                                        el)
+        self.cape = SoundingParams.find_cape(virtual_temp_line,
+                                             moist_adiabat,
+                                             lfc,
+                                             el)
 
         self.temp_line         = temp_line
         self.virtual_temp_line = virtual_temp_line