diff --git a/alyx/actions/admin.py b/alyx/actions/admin.py
index 8d08f5ef..ab69393c 100644
--- a/alyx/actions/admin.py
+++ b/alyx/actions/admin.py
@@ -416,14 +416,8 @@ class WaterTypeAdmin(BaseActionAdmin):
     list_display_links = ('name',)
 
 
-class SurgeryActionForm(BaseActionForm):
-    def __init__(self, *args, **kwargs):
-        super().__init__(*args, **kwargs)
-        self.fields['implant_weight'].required = True
-
-
 class SurgeryAdmin(BaseActionAdmin):
-    form = SurgeryActionForm
+    form = BaseActionForm
     list_display = ['subject_l', 'date', 'users_l', 'procedures_l',
                     'narrative', 'projects', 'implant_weight']
     list_select_related = ('subject',)
diff --git a/alyx/actions/migrations/0026_alter_surgery_implant_weight.py b/alyx/actions/migrations/0026_alter_surgery_implant_weight.py
new file mode 100644
index 00000000..8cb40635
--- /dev/null
+++ b/alyx/actions/migrations/0026_alter_surgery_implant_weight.py
@@ -0,0 +1,19 @@
+# Generated by Django 5.1.2 on 2024-11-19 14:14
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('actions', '0025_move_implant_weight'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='surgery',
+            name='implant_weight',
+            field=models.FloatField(help_text='Implant weight in grams', validators=[django.core.validators.MinValueValidator(0)]),
+        ),
+    ]
diff --git a/alyx/actions/models.py b/alyx/actions/models.py
index 488cfb54..8c08e959 100644
--- a/alyx/actions/models.py
+++ b/alyx/actions/models.py
@@ -203,7 +203,7 @@ class Surgery(BaseAction):
                                  default=_default_surgery_location,
                                  help_text="The physical location at which the surgery was "
                                  "performed")
-    implant_weight = models.FloatField(null=False, blank=True, validators=[MinValueValidator(0)],
+    implant_weight = models.FloatField(null=False, blank=False, validators=[MinValueValidator(0)],
                                        help_text="Implant weight in grams")
 
     class Meta:
diff --git a/alyx/alyx/__init__.py b/alyx/alyx/__init__.py
index 82a1aec7..90db8dcc 100644
--- a/alyx/alyx/__init__.py
+++ b/alyx/alyx/__init__.py
@@ -1 +1 @@
-VERSION = __version__ = '3.1.0'
+VERSION = __version__ = '3.1.1'
diff --git a/alyx/jobs/admin.py b/alyx/jobs/admin.py
index 7c2dad0b..0114cea4 100644
--- a/alyx/jobs/admin.py
+++ b/alyx/jobs/admin.py
@@ -29,7 +29,7 @@ def has_change_permission(self, request, obj=None):
         if obj:
             if obj.session:
                 # Check if session user or member of the same lab
-                is_session_user = obj.session.users.users.contains(request.user)
+                is_session_user = obj.session.users.contains(request.user)
                 return is_session_user or obj.session.lab.name in request.user.lab
             else:
                 # Check if user is member of the lab associated with the task repository
diff --git a/alyx/subjects/admin.py b/alyx/subjects/admin.py
index 5c736786..e1ac3b28 100755
--- a/alyx/subjects/admin.py
+++ b/alyx/subjects/admin.py
@@ -20,7 +20,7 @@
                      )
 from actions.models import (
     Surgery, Session, OtherAction, WaterAdministration, WaterRestriction, Weighing)
-from actions.admin import SurgeryActionForm
+from actions.admin import BaseActionForm
 from misc.models import LabMember, Housing
 from misc.admin import NoteInline
 
@@ -236,7 +236,7 @@ def has_add_permission(self, request, obj=None):
 
 
 class AddSurgeryInline(SurgeryInline):
-    form = SurgeryActionForm
+    form = BaseActionForm
     readonly_fields = ()
     show_change_link = False
     verbose_name = "New surgery"