diff --git a/app/models/notification.rb b/app/models/notification.rb
index f1605f034..ae7c782be 100644
--- a/app/models/notification.rb
+++ b/app/models/notification.rb
@@ -180,8 +180,8 @@ class Notification < ApplicationRecord
     # Notifications that have no `group_key` each count as a separate group.
     def paginate_groups_by_max_id(limit, max_id: nil, since_id: nil)
       query = reorder(id: :desc)
-      query = query.where(id: ...max_id) if max_id.present?
-      query = query.where(id: (since_id + 1)...) if since_id.present?
+      query = query.where(id: ...(max_id.to_i)) if max_id.present?
+      query = query.where(id: (since_id.to_i + 1)...) if since_id.present?
       query.paginate_groups(limit, :desc)
     end
 
@@ -190,8 +190,8 @@ class Notification < ApplicationRecord
     # Results will be in ascending order by id.
     def paginate_groups_by_min_id(limit, max_id: nil, min_id: nil)
       query = reorder(id: :asc)
-      query = query.where(id: (min_id + 1)...) if min_id.present?
-      query = query.where(id: ...max_id) if max_id.present?
+      query = query.where(id: (min_id.to_i + 1)...) if min_id.present?
+      query = query.where(id: ...(max_id.to_i)) if max_id.present?
       query.paginate_groups(limit, :asc)
     end
 
diff --git a/spec/requests/api/v2_alpha/notifications_spec.rb b/spec/requests/api/v2_alpha/notifications_spec.rb
index 94bc7b0ee..a613158aa 100644
--- a/spec/requests/api/v2_alpha/notifications_spec.rb
+++ b/spec/requests/api/v2_alpha/notifications_spec.rb
@@ -97,8 +97,7 @@ RSpec.describe 'Notifications' do
     before do
       first_status = PostStatusService.new.call(user.account, text: 'Test')
       ReblogService.new.call(bob.account, first_status)
-      mentioning_status = PostStatusService.new.call(bob.account, text: 'Hello @alice')
-      mentioning_status.mentions.first
+      PostStatusService.new.call(bob.account, text: 'Hello @alice')
       FavouriteService.new.call(bob.account, first_status)
       FavouriteService.new.call(tom.account, first_status)
       FollowService.new.call(bob.account, user.account)
@@ -141,18 +140,37 @@ RSpec.describe 'Notifications' do
 
     context 'with limit param' do
       let(:params) { { limit: 3 } }
+      let(:notifications) { user.account.notifications.reorder(id: :desc) }
 
       it 'returns the requested number of notifications paginated', :aggregate_failures do
         subject
 
-        notifications = user.account.notifications
-
         expect(body_as_json[:notification_groups].size)
           .to eq(params[:limit])
 
         expect(response)
           .to include_pagination_headers(
-            prev: api_v2_alpha_notifications_url(limit: params[:limit], min_id: notifications.last.id),
+            prev: api_v2_alpha_notifications_url(limit: params[:limit], min_id: notifications.first.id),
+            # TODO: one downside of the current approach is that we return the first ID matching the group,
+            # not the last that has been skipped, so pagination is very likely to give overlap
+            next: api_v2_alpha_notifications_url(limit: params[:limit], max_id: notifications[3].id)
+          )
+      end
+    end
+
+    context 'with since_id param' do
+      let(:params) { { since_id: notifications[2].id } }
+      let(:notifications) { user.account.notifications.reorder(id: :desc) }
+
+      it 'returns the requested number of notifications paginated', :aggregate_failures do
+        subject
+
+        expect(body_as_json[:notification_groups].size)
+          .to eq(2)
+
+        expect(response)
+          .to include_pagination_headers(
+            prev: api_v2_alpha_notifications_url(limit: params[:limit], min_id: notifications.first.id),
             # TODO: one downside of the current approach is that we return the first ID matching the group,
             # not the last that has been skipped, so pagination is very likely to give overlap
             next: api_v2_alpha_notifications_url(limit: params[:limit], max_id: notifications[1].id)