diff --git a/app/finders/events_finder.rb b/app/finders/events_finder.rb
index 2e82bda8730fc5b360ce0e99371771705b1fc740..8df01f1dad9444fd3cc7128110d5646a3fd5f416 100644
--- a/app/finders/events_finder.rb
+++ b/app/finders/events_finder.rb
@@ -58,7 +58,7 @@ class EventsFinder
   def by_target_type(events)
     return events unless Event::TARGET_TYPES[params[:target_type]]
 
-    events.where(target_type: Event::TARGET_TYPES[params[:target_type]])
+    events.where(target_type: Event::TARGET_TYPES[params[:target_type]].name)
   end
   # rubocop: enable CodeReuse/ActiveRecord
 
diff --git a/app/models/ci/build.rb b/app/models/ci/build.rb
index 889f8ce27a6e22b696ef24dc493242afd82f5b87..ac02bab1169f88d38c84e7b5d24c0eb57a191c6a 100644
--- a/app/models/ci/build.rb
+++ b/app/models/ci/build.rb
@@ -98,7 +98,7 @@ module Ci
 
     scope :matches_tag_ids, -> (tag_ids) do
       matcher = ::ActsAsTaggableOn::Tagging
-        .where(taggable_type: CommitStatus)
+        .where(taggable_type: CommitStatus.name)
         .where(context: 'tags')
         .where('taggable_id = ci_builds.id')
         .where.not(tag_id: tag_ids).select('1')
@@ -108,7 +108,7 @@ module Ci
 
     scope :with_any_tags, -> do
       matcher = ::ActsAsTaggableOn::Tagging
-        .where(taggable_type: CommitStatus)
+        .where(taggable_type: CommitStatus.name)
         .where(context: 'tags')
         .where('taggable_id = ci_builds.id').select('1')
 
diff --git a/app/models/concerns/avatarable.rb b/app/models/concerns/avatarable.rb
index 0d5311a99859c152e9bac601fa8a459c3a56b663..b42236c1fa216a0a753d834bbcad650ed052e500 100644
--- a/app/models/concerns/avatarable.rb
+++ b/app/models/concerns/avatarable.rb
@@ -86,7 +86,7 @@ module Avatarable
         params[:model].upload_paths(params[:identifier])
       end
 
-      Upload.where(uploader: AvatarUploader, path: paths).find_each do |upload|
+      Upload.where(uploader: AvatarUploader.name, path: paths).find_each do |upload|
         model = model_class.instantiate('id' => upload.model_id)
 
         loader.call({ model: model, identifier: File.basename(upload.path) }, upload)
diff --git a/app/services/todos/destroy/entity_leave_service.rb b/app/services/todos/destroy/entity_leave_service.rb
index e8d1bcdd142dd752f7dd561a53d208d1c25ee9bf..ebfb20132d021e6206e8bc04bc0209dd2ff6a6d1 100644
--- a/app/services/todos/destroy/entity_leave_service.rb
+++ b/app/services/todos/destroy/entity_leave_service.rb
@@ -45,7 +45,7 @@ module Todos
       # rubocop: disable CodeReuse/ActiveRecord
       def remove_confidential_issue_todos
         Todo.where(
-          target_id: confidential_issues.select(:id), target_type: Issue, user_id: user.id
+          target_id: confidential_issues.select(:id), target_type: Issue.name, user_id: user.id
         ).delete_all
       end
       # rubocop: enable CodeReuse/ActiveRecord
diff --git a/app/services/todos/destroy/private_features_service.rb b/app/services/todos/destroy/private_features_service.rb
index a8c3fe0ef5a43267342a41f32d3cba5b1040f21d..bd49519d694db7dfc08ec0dcee789a1655036a88 100644
--- a/app/services/todos/destroy/private_features_service.rb
+++ b/app/services/todos/destroy/private_features_service.rb
@@ -14,9 +14,9 @@ module Todos
       def execute
         ProjectFeature.where(project_id: project_ids).each do |project_features|
           target_types = []
-          target_types << Issue if private?(project_features.issues_access_level)
-          target_types << MergeRequest if private?(project_features.merge_requests_access_level)
-          target_types << Commit if private?(project_features.repository_access_level)
+          target_types << Issue.name if private?(project_features.issues_access_level)
+          target_types << MergeRequest.name if private?(project_features.merge_requests_access_level)
+          target_types << Commit.name if private?(project_features.repository_access_level)
 
           next if target_types.empty?
 
diff --git a/changelogs/unreleased/rails5-active-record-class-value.yml b/changelogs/unreleased/rails5-active-record-class-value.yml
new file mode 100644
index 0000000000000000000000000000000000000000..9f9fdf10cd1e12b65428c7b91885f5c6da83196b
--- /dev/null
+++ b/changelogs/unreleased/rails5-active-record-class-value.yml
@@ -0,0 +1,5 @@
+---
+title: 'Rails5: Passing a class as a value in an Active Record query is deprecated'
+merge_request: 23164
+author: Jasper Maes
+type: other
diff --git a/spec/finders/pending_todos_finder_spec.rb b/spec/finders/pending_todos_finder_spec.rb
index 32fad5e225f669391a9019a996f603386940c60e..b41b1b46a939b9017b0b5be4b6b9778e7f8e85c7 100644
--- a/spec/finders/pending_todos_finder_spec.rb
+++ b/spec/finders/pending_todos_finder_spec.rb
@@ -46,7 +46,7 @@ describe PendingTodosFinder do
 
       create(:todo, :pending, user: user, target: note)
 
-      todos = described_class.new(user, target_type: issue.class).execute
+      todos = described_class.new(user, target_type: issue.class.name).execute
 
       expect(todos).to eq([todo])
     end
diff --git a/spec/models/todo_spec.rb b/spec/models/todo_spec.rb
index 2c01578aaca94f6b7a2e7f83bb13dc3ec78a4134..82ff2a002e004927ddf579b3bf48b0a33c8546a7 100644
--- a/spec/models/todo_spec.rb
+++ b/spec/models/todo_spec.rb
@@ -226,7 +226,7 @@ describe Todo do
 
       create(:todo, target: create(:merge_request))
 
-      expect(described_class.for_type(Issue)).to eq([todo])
+      expect(described_class.for_type(Issue.name)).to eq([todo])
     end
   end