diff --git a/scripts/python-skywater-pdk/skywater_pdk/corners.py b/scripts/python-skywater-pdk/skywater_pdk/corners.py
index a464d5c..1b08078 100644
--- a/scripts/python-skywater-pdk/skywater_pdk/corners.py
+++ b/scripts/python-skywater-pdk/skywater_pdk/corners.py
@@ -20,10 +20,14 @@
 
 
 CornerTypeMappings = {}
-# "fs" is sometimes called "wp" meaning worst-case power,
-CornerTypeMappings["wp"] = "fs"
-# "sf" is sometimes called "ws" meaning worst-case speed
-CornerTypeMappings["ws"] = "sf"
+# "wo" is "worst-case one" and corresponds to "fs"
+CornerTypeMappings["wo"] = "fs"
+# "wz" is "worst-case zero" and corresponds to "sf"
+CornerTypeMappings["wz"] = "sf"
+# "wp" is "worst-case power" and corresponds to "ff"
+CornerTypeMappings["wp"] = "ff"
+# "ws" is "worst-case speed" and corresponds to "ss"
+CornerTypeMappings["ws"] = "ss"
 
 
 class CornerType(Flag):
@@ -44,10 +48,13 @@
         if s in CornerTypeMappings:
             return cls.parse(CornerTypeMappings[s])
         if len(s) > 1:
-            o = []
-            for c in s:
-                o.append(cls.parse(c))
-            return o
+            try:
+                o = []
+                for c in s:
+                    o.append(cls.parse(c))
+                return o
+            except TypeError:
+                raise TypeError("Unknown corner type: {}".format(s))
         if not hasattr(cls, s):
             raise TypeError("Unknown corner type: {}".format(s))
         return getattr(cls, s)