diff --git a/pyproject.toml b/pyproject.toml
index 06b80167..8594ee83 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -71,7 +71,7 @@ test-mindeps = [
     "typing_extensions==4.0",
 ]
 typing = [
-    "mypy==1.19.1",
+    "mypy==2.1.0",
     "types-jwt",
     "types-requests",
     "types-jmespath",
diff --git a/src/globus_cli/commands/flows/_common.py b/src/globus_cli/commands/flows/_common.py
index fec38c7e..24e574c8 100644
--- a/src/globus_cli/commands/flows/_common.py
+++ b/src/globus_cli/commands/flows/_common.py
@@ -131,13 +131,21 @@ class SubscriptionIdType(
     name = "SUBSCRIPTION_ID"
 
     def __init__(self, *, omittable: bool = False) -> None:
-        self._omittable = omittable
+        self._omittable: bool = omittable
 
     def convert(
-        self, value: t.Any, param: click.Parameter | None, ctx: click.Context | None
+        self,
+        value: t.Any | globus_sdk.MissingType,
+        param: click.Parameter | None,
+        ctx: click.Context | None,
     ) -> uuid.UUID | t.Literal["DEFAULT"] | globus_sdk.MissingType:
-        if self._omittable and value is globus_sdk.MISSING:
-            return globus_sdk.MISSING
+        if value is globus_sdk.MISSING:
+            if self._omittable:
+                return globus_sdk.MISSING
+            else:
+                raise NotImplementedError(
+                    "Cannot pass MISSING to non-omittable SubscriptionidType."
+                )
 
         if value.upper() == "DEFAULT":
             return "DEFAULT"
diff --git a/src/globus_cli/parsing/param_types/delimited.py b/src/globus_cli/parsing/param_types/delimited.py
index 8a0098c3..a7586f88 100644
--- a/src/globus_cli/parsing/param_types/delimited.py
+++ b/src/globus_cli/parsing/param_types/delimited.py
@@ -28,12 +28,18 @@ def get_metavar(self, param: click.Parameter, ctx: click.Context) -> str:
         return "TEXT,TEXT,..."
 
     def convert(
-        self, value: t.Any, param: click.Parameter | None, ctx: click.Context | None
+        self,
+        value: t.Any | globus_sdk.MissingType,
+        param: click.Parameter | None,
+        ctx: click.Context | None,
     ) -> list[str] | globus_sdk.MissingType:
-        if self._omittable and value is globus_sdk.MISSING:
-            return globus_sdk.MISSING
-
-        value = super().convert(value, param, ctx)
+        if value is globus_sdk.MISSING:
+            if self._omittable:
+                return globus_sdk.MISSING
+            else:
+                raise NotImplementedError(
+                    "Cannot pass MISSING to non-omittable CommaDelimitedList."
+                )
 
         # if `--foo` is a comma delimited list and someone passes
         # `--foo ""`, take that as `foo=[]` rather than foo=[""]
diff --git a/src/globus_cli/parsing/param_types/omittable.py b/src/globus_cli/parsing/param_types/omittable.py
index c466dedc..af9d5e70 100644
--- a/src/globus_cli/parsing/param_types/omittable.py
+++ b/src/globus_cli/parsing/param_types/omittable.py
@@ -12,7 +12,10 @@ class OmittableInt(click.ParamType[int | globus_sdk.MissingType]):
     name = "integer"
 
     def convert(
-        self, value: t.Any, param: click.Parameter | None, ctx: click.Context | None
+        self,
+        value: t.Any | globus_sdk.MissingType,
+        param: click.Parameter | None,
+        ctx: click.Context | None,
     ) -> int | globus_sdk.MissingType:
         if value is globus_sdk.MISSING:
             return globus_sdk.MISSING
@@ -26,7 +29,10 @@ class OmittableString(click.ParamType[str | globus_sdk.MissingType]):
     name = "text"
 
     def convert(
-        self, value: t.Any, param: click.Parameter | None, ctx: click.Context | None
+        self,
+        value: t.Any | globus_sdk.MissingType,
+        param: click.Parameter | None,
+        ctx: click.Context | None,
     ) -> str | globus_sdk.MissingType:
         if value is globus_sdk.MISSING:
             return globus_sdk.MISSING
@@ -40,7 +46,10 @@ class OmittableUUID(click.ParamType[uuid.UUID | globus_sdk.MissingType]):
     name = "uuid"
 
     def convert(
-        self, value: t.Any, param: click.Parameter | None, ctx: click.Context | None
+        self,
+        value: t.Any | globus_sdk.MissingType,
+        param: click.Parameter | None,
+        ctx: click.Context | None,
     ) -> uuid.UUID | globus_sdk.MissingType:
         if value is globus_sdk.MISSING:
             return globus_sdk.MISSING
@@ -65,7 +74,10 @@ def get_missing_message(
         return self._inner_choice.get_missing_message(param, ctx)
 
     def convert(
-        self, value: t.Any, param: click.Parameter | None, ctx: click.Context | None
+        self,
+        value: t.Any | globus_sdk.MissingType,
+        param: click.Parameter | None,
+        ctx: click.Context | None,
     ) -> str | globus_sdk.MissingType:
         if value is globus_sdk.MISSING:
             return globus_sdk.MISSING
@@ -92,7 +104,10 @@ class OmittableDateTime(_OmittableDateTimeBase):
     name = "datetime"
 
     def convert(
-        self, value: t.Any, param: click.Parameter | None, ctx: click.Context | None
+        self,
+        value: t.Any | globus_sdk.MissingType,
+        param: click.Parameter | None,
+        ctx: click.Context | None,
     ) -> datetime.datetime | globus_sdk.MissingType:
         if value is globus_sdk.MISSING:
             return globus_sdk.MISSING