diff --git a/changelogs/unreleased/22951-fix-todos-api-endpoint-error-for-commits.yml b/changelogs/unreleased/22951-fix-todos-api-endpoint-error-for-commits.yml
new file mode 100644
index 00000000000..a53e7d77c16
--- /dev/null
+++ b/changelogs/unreleased/22951-fix-todos-api-endpoint-error-for-commits.yml
@@ -0,0 +1,4 @@
+---
+title: Add spec for todo with target_type Commit
+merge_request: 9351
+author: George Andrinopoulos
diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index a99d9cadc8a..b839d72a0e1 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -394,7 +394,8 @@ module API
       expose :target_type
 
       expose :target do |todo, options|
-        Entities.const_get(todo.target_type).represent(todo.target, options)
+        target = todo.target_type == 'Commit' ? 'RepoCommit' : todo.target_type
+        Entities.const_get(target).represent(todo.target, options)
       end
 
       expose :target_url do |todo, options|
diff --git a/spec/factories/todos.rb b/spec/factories/todos.rb
index a5265f1b189..c1ac3bb84ad 100644
--- a/spec/factories/todos.rb
+++ b/spec/factories/todos.rb
@@ -18,11 +18,6 @@ FactoryGirl.define do
       action { Todo::DIRECTLY_ADDRESSED }
     end
 
-    trait :on_commit do
-      commit_id RepoHelpers.sample_commit.id
-      target_type "Commit"
-    end
-
     trait :build_failed do
       action { Todo::BUILD_FAILED }
       target factory: :merge_request
@@ -48,4 +43,13 @@ FactoryGirl.define do
       state :done
     end
   end
+
+  factory :on_commit_todo, class: Todo do
+    project factory: :empty_project
+    author
+    user
+    action { Todo::ASSIGNED }
+    commit_id RepoHelpers.sample_commit.id
+    target_type "Commit"
+  end
 end
diff --git a/spec/requests/api/todos_spec.rb b/spec/requests/api/todos_spec.rb
index f35e963a14b..1e401935662 100644
--- a/spec/requests/api/todos_spec.rb
+++ b/spec/requests/api/todos_spec.rb
@@ -3,7 +3,7 @@ require 'spec_helper'
 describe API::Todos, api: true do
   include ApiHelpers
 
-  let(:project_1) { create(:empty_project) }
+  let(:project_1) { create(:empty_project, :test_repo) }
   let(:project_2) { create(:empty_project) }
   let(:author_1) { create(:user) }
   let(:author_2) { create(:user) }
@@ -11,7 +11,7 @@ describe API::Todos, api: true do
   let(:merge_request) { create(:merge_request, source_project: project_1) }
   let!(:pending_1) { create(:todo, :mentioned, project: project_1, author: author_1, user: john_doe) }
   let!(:pending_2) { create(:todo, project: project_2, author: author_2, user: john_doe) }
-  let!(:pending_3) { create(:todo, project: project_1, author: author_2, user: john_doe) }
+  let!(:pending_3) { create(:on_commit_todo, project: project_1, author: author_2, user: john_doe) }
   let!(:done) { create(:todo, :done, project: project_1, author: author_1, user: john_doe) }
 
   before do