diff --git a/backend/sophon/core/tests.py b/backend/sophon/core/tests.py
index 520dd88..00d0c1a 100644
--- a/backend/sophon/core/tests.py
+++ b/backend/sophon/core/tests.py
@@ -95,6 +95,9 @@ class ReadSophonTestCase(BetterAPITestCase, metaclass=abc.ABCMeta):
         except errors.HTTPException as exc:
             self.assertEqual(exc.status, code, msg=f"`list` did not return {code}: {exc!r}")
             return None
+        except ValueError as exc:
+            self.assertEqual(400, code, msg=f"`list` did not return {code}: {exc!r}")
+            return None
         else:
             self.assertEqual(response.status_code, code, msg=f"`list` did not return {code}: {response.data!r}")
             return response.data or None
@@ -122,6 +125,9 @@ class ReadSophonTestCase(BetterAPITestCase, metaclass=abc.ABCMeta):
         except errors.HTTPException as exc:
             self.assertEqual(exc.status, code, msg=f"`retrieve` did not return {code}: {exc!r}")
             return None
+        except ValueError as exc:
+            self.assertEqual(400, code, msg=f"`retrieve` did not return {code}: {exc!r}")
+            return None
         else:
             self.assertEqual(response.status_code, code, msg=f"`retrieve` did not return {code}: {response.data!r}")
             return response.data
@@ -153,6 +159,9 @@ class ReadSophonTestCase(BetterAPITestCase, metaclass=abc.ABCMeta):
         except errors.HTTPException as exc:
             self.assertEqual(exc.status, code, msg=f"`{action}` did not return {code}: {exc!r}")
             return None
+        except ValueError as exc:
+            self.assertEqual(400, code, msg=f"`{action}` did not return {code}: {exc!r}")
+            return None
         else:
             self.assertEqual(response.status_code, code, msg=f"`{action}` did not return {code}: {response.data!r}")
             return response.data
@@ -186,6 +195,9 @@ class ReadSophonTestCase(BetterAPITestCase, metaclass=abc.ABCMeta):
         except errors.HTTPException as exc:
             self.assertEqual(exc.status, code, msg=f"`{action}` did not return {code}: {exc!r}")
             return None
+        except ValueError as exc:
+            self.assertEqual(400, code, msg=f"`{action}` did not return {code}: {exc!r}")
+            return None
         else:
             self.assertEqual(response.status_code, code, msg=f"`{action}` did not return {code}: {response.data!r}")
             return response.data
@@ -219,6 +231,9 @@ class WriteSophonTestCase(ReadSophonTestCase, metaclass=abc.ABCMeta):
         except errors.HTTPException as exc:
             self.assertEqual(exc.status, code, msg=f"`create` did not return {code}: {exc!r}")
             return None
+        except ValueError as exc:
+            self.assertEqual(400, code, msg=f"`create` did not return {code}: {exc!r}")
+            return None
         else:
             self.assertEqual(response.status_code, code, msg=f"`create` did not return {code}: {response.data!r}")
             return response.data
@@ -248,6 +263,9 @@ class WriteSophonTestCase(ReadSophonTestCase, metaclass=abc.ABCMeta):
         except errors.HTTPException as exc:
             self.assertEqual(exc.status, code, msg=f"`update` did not return {code}: {exc!r}")
             return None
+        except ValueError as exc:
+            self.assertEqual(400, code, msg=f"`update` did not return {code}: {exc!r}")
+            return None
         else:
             self.assertEqual(response.status_code, code, msg=f"`update` did not return {code}: {response.data!r}")
             return response.data
@@ -273,7 +291,10 @@ class WriteSophonTestCase(ReadSophonTestCase, metaclass=abc.ABCMeta):
         try:
             response = self.destroy(pk=pk)
         except errors.HTTPException as exc:
-            self.assertEqual(exc.status, code, msg=f"`create` did not return {code}: {exc!r}")
+            self.assertEqual(exc.status, code, msg=f"`destroy` did not return {code}: {exc!r}")
+            return None
+        except ValueError as exc:
+            self.assertEqual(400, code, msg=f"`destroy` did not return {code}: {exc!r}")
             return None
         else:
             self.assertEqual(response.status_code, code, msg=f"`destroy` did not return {code}: {response.data!r}")
@@ -317,11 +338,6 @@ class UsersByIdTestCase(ReadSophonTestCase):
         data = self.assertActionRetrieve(self.third_user.id)
         self.assertData(data, {"username": "third"})
 
-    def test_retrieve_400(self):
-        self.assertActionRetrieve("qwerty", code=400)
-        self.assertActionRetrieve(1.0, code=400)
-        self.assertActionRetrieve("xyzzy", code=400)
-
     def test_retrieve_404(self):
         self.assertActionRetrieve(100, code=404)
         self.assertActionRetrieve(-1, code=404)
@@ -365,11 +381,6 @@ class UsersByUsernameTestCase(ReadSophonTestCase):
         data = self.assertActionRetrieve(self.third_user.username)
         self.assertData(data, {"username": "aaaaaa"})
 
-    def test_retrieve_400(self):
-        self.assertActionRetrieve(1, code=400)
-        self.assertActionRetrieve(-1, code=400)
-        self.assertActionRetrieve(1.0, code=400)
-
     def test_retrieve_404(self):
         self.assertActionRetrieve("sas", code=404)
         self.assertActionRetrieve("sos", code=404)
diff --git a/backend/sophon/core/views.py b/backend/sophon/core/views.py
index 9a20695..748d940 100644
--- a/backend/sophon/core/views.py
+++ b/backend/sophon/core/views.py
@@ -4,6 +4,7 @@ import typing as t
 import deprecation
 from django.contrib.auth.models import User
 from django.db.models import QuerySet
+from django.shortcuts import get_object_or_404
 from rest_framework import status as s
 from rest_framework.decorators import action
 from rest_framework.request import Request
@@ -195,7 +196,7 @@ class UsersByIdViewSet(ReadSophonViewSet):
 
     def get_object(self):
         pk = self.kwargs["pk"]
-        return User.objects.filter(id=pk).get()
+        return get_object_or_404(User.objects.filter(id=pk))
 
 
 class UsersByUsernameViewSet(ReadSophonViewSet):
@@ -211,7 +212,7 @@ class UsersByUsernameViewSet(ReadSophonViewSet):
 
     def get_object(self):
         pk = self.kwargs["pk"]
-        return User.objects.filter(username=pk).get()
+        return get_object_or_404(User.objects.filter(username=pk))
 
 
 class ResearchGroupViewSet(WriteSophonViewSet):
@@ -260,7 +261,7 @@ class ResearchGroupViewSet(WriteSophonViewSet):
         """
         An action that allows an user to join a group with ``"OPEN"`` access.
         """
-        group = models.ResearchGroup.objects.get(pk=pk)
+        group = get_object_or_404(models.ResearchGroup.objects, pk=pk)
 
         if self.request.user.is_anonymous:
             return Response(status=s.HTTP_401_UNAUTHORIZED)
@@ -284,7 +285,7 @@ class ResearchGroupViewSet(WriteSophonViewSet):
 
         Group owners aren't allowed to leave the group they created to prevent situations where a group has no owner.
         """
-        group = models.ResearchGroup.objects.get(pk=pk)
+        group = get_object_or_404(models.ResearchGroup.objects, pk=pk)
 
         if self.request.user.is_anonymous:
             return Response(status=s.HTTP_401_UNAUTHORIZED)