diff --git a/pywidevine/pssh.py b/pywidevine/pssh.py
index 29e651e..2eae1fe 100644
--- a/pywidevine/pssh.py
+++ b/pywidevine/pssh.py
@@ -170,25 +170,6 @@ class PSSH:
             if init_data is None and key_ids is None:
                 raise ValueError("Version 1 PSSH boxes must use either init_data or key_ids but neither were provided")
 
-        if key_ids is not None:
-            # ensure key_ids are UUID, supports hex, base64, and bytes
-            if not all(isinstance(x, (UUID, bytes, str)) for x in key_ids):
-                not_bytes = [x for x in key_ids if not isinstance(x, (UUID, bytes, str))]
-                raise TypeError(
-                    "Expected all of key_ids to be a UUID, hex, base64, or bytes, but one or more are not, "
-                    f"{not_bytes!r}"
-                )
-            key_ids = [
-                UUID(bytes=key_id_b)
-                for key_id in key_ids
-                for key_id_b in [
-                    key_id.bytes if isinstance(key_id, UUID) else
-                    bytes.fromhex(key_id) if all(c in string.hexdigits for c in key_id) else
-                    base64.b64decode(key_id) if isinstance(key_id, str) else
-                    key_id
-                ]
-            ]
-
         if init_data is not None:
             if isinstance(init_data, WidevinePsshData):
                 init_data = init_data.SerializeToString()
@@ -217,7 +198,7 @@ class PSSH:
             # The version must be reinforced ONLY if we have key_id data or there's a possibility of making
             # a v1 PSSH box, that did not have key_IDs set in the PSSH box.
             pssh.version = version
-            pssh.set_key_ids(key_ids)
+            pssh.set_key_ids(cls.parse_key_ids(key_ids))
 
         return pssh
 
@@ -430,3 +411,32 @@ class PSSH:
         ]
 
         self.init_data = cenc_header.SerializeToString()
+
+    @staticmethod
+    def parse_key_ids(key_ids: list[Union[UUID, str, bytes]]) -> list[UUID]:
+        """
+        Parse a list of Key IDs in hex, base64, or bytes to UUIDs.
+
+        Raises TypeError if `key_ids` is not a list, or the list contains one
+        or more items that are not a UUID, str, or bytes object.
+        """
+        if not isinstance(key_ids, list):
+            raise TypeError(f"Expected key_ids to be a list, not {key_ids!r}")
+
+        if not all(isinstance(x, (UUID, str, bytes)) for x in key_ids):
+            raise TypeError("Some items of key_ids are not a UUID, str, or bytes. Unsure how to continue...")
+
+        uuids = [
+            UUID(bytes=key_id_b)
+            for key_id in key_ids
+            for key_id_b in [
+                key_id.bytes if isinstance(key_id, UUID) else
+                (
+                    bytes.fromhex(key_id) if all(c in string.hexdigits for c in key_id) else
+                    base64.b64decode(key_id)
+                ) if isinstance(key_id, str) else
+                key_id
+            ]
+        ]
+
+        return uuids