diff --git a/pypitoken/restrictions.py b/pypitoken/restrictions.py
index c9849ad..8c97a72 100644
--- a/pypitoken/restrictions.py
+++ b/pypitoken/restrictions.py
@@ -371,11 +371,16 @@ def check(self, context: Context) -> None:
     @classmethod
     def from_parameters(
         cls,
-        project_names: list[str] | None = None,
+        project_names: Iterable[str] | None = None,
         **kwargs,
     ) -> ProjectNamesRestriction | None:
         if project_names is not None:
-            return cls(project_names=project_names)
+            if isinstance(project_names, str):
+                raise exceptions.InvalidRestriction(
+                    "project_names should be an iterable of strings. "
+                    "Received a single string not wrapped in an iterable."
+                )
+            return cls(project_names=list(project_names))
         return None
 
 
@@ -435,11 +440,16 @@ def check(self, context: Context) -> None:
     @classmethod
     def from_parameters(
         cls,
-        project_ids: list[str] | None = None,
+        project_ids: Iterable[str] | None = None,
         **kwargs,
     ) -> ProjectIDsRestriction | None:
         if project_ids is not None:
-            return cls(project_ids=project_ids)
+            if isinstance(project_ids, str):
+                raise exceptions.InvalidRestriction(
+                    "project_ids should be an iterable of strings. "
+                    "Received a single string not wrapped in an iterable."
+                )
+            return cls(project_ids=list(project_ids))
         return None
 
 
@@ -598,11 +608,16 @@ def check(self, context: Context) -> None:
     @classmethod
     def from_parameters(
         cls,
-        legacy_project_names: list[str] | None = None,
+        legacy_project_names: Iterable[str] | None = None,
         **kwargs,
     ) -> LegacyProjectNamesRestriction | None:
         if legacy_project_names is not None:
-            return cls(project_names=legacy_project_names)
+            if isinstance(legacy_project_names, str):
+                raise exceptions.InvalidRestriction(
+                    "legacy_project_names should be an iterable of strings. "
+                    "Received a single string not wrapped in an iterable."
+                )
+            return cls(project_names=list(legacy_project_names))
         return None
 
 
diff --git a/pypitoken/token.py b/pypitoken/token.py
index 4c8457b..869af59 100644
--- a/pypitoken/token.py
+++ b/pypitoken/token.py
@@ -2,6 +2,7 @@
 
 import datetime
 import functools
+from typing import Iterable
 
 import pymacaroons
 from typing_extensions import ParamSpec
@@ -152,11 +153,11 @@ def restrict(
         self,
         not_before: int | datetime.datetime | None = None,
         not_after: int | datetime.datetime | None = None,
-        project_names: list[str] | None = None,
-        project_ids: list[str] | None = None,
+        project_names: Iterable[str] | None = None,
+        project_ids: Iterable[str] | None = None,
         user_id: str | None = None,
         # Legacy params
-        legacy_project_names: list[str] | None = None,
+        legacy_project_names: Iterable[str] | None = None,
         legacy_not_before: int | datetime.datetime | None = None,
         legacy_not_after: int | datetime.datetime | None = None,
         legacy_noop: bool | None = None,
diff --git a/tests/test_restrictions.py b/tests/test_restrictions.py
index bf861d0..6ba85c5 100644
--- a/tests/test_restrictions.py
+++ b/tests/test_restrictions.py
@@ -198,6 +198,13 @@ def test__LegacyProjectNamesRestriction__from_parameters__not_empty():
     ) == restrictions.LegacyProjectNamesRestriction(project_names=["a", "b"])
 
 
+def test__LegacyProjectNamesRestriction__from_parameters__bare_string():
+    with pytest.raises(exceptions.InvalidRestriction):
+        restrictions.LegacyProjectNamesRestriction.from_parameters(
+            legacy_project_names="a"
+        )
+
+
 def test__LegacyDateRestriction__load_value__pass():
     assert restrictions.LegacyDateRestriction._load_value(
         value={"nbf": 1_234_567_890, "exp": 1_234_567_900}
@@ -546,6 +553,11 @@ def test__ProjectNamesRestriction__from_parameters__empty():
     assert restrictions.ProjectNamesRestriction.from_parameters() is None
 
 
+def test__ProjectNamesRestriction__from_parameters__bare_string():
+    with pytest.raises(exceptions.InvalidRestriction):
+        restrictions.ProjectNamesRestriction.from_parameters(project_names="a")
+
+
 def test__ProjectNamesRestriction__from_parameters__not_empty():
     assert restrictions.ProjectNamesRestriction.from_parameters(
         project_names=["a", "b"]
@@ -669,6 +681,13 @@ def test__ProjectIDsRestriction__from_parameters__empty():
     assert restrictions.ProjectIDsRestriction.from_parameters() is None
 
 
+def test__ProjectIDsRestriction__from_parameters__bare_string():
+    with pytest.raises(exceptions.InvalidRestriction):
+        restrictions.ProjectIDsRestriction.from_parameters(
+            project_ids="00000000-0000-0000-0000-000000000000"
+        )
+
+
 def test__ProjectIDsRestriction__from_parameters__not_empty():
     assert restrictions.ProjectIDsRestriction.from_parameters(
         project_ids=[