diff --git a/app/controllers/settings/github_syncer_controller.rb b/app/controllers/settings/github_syncer_controller.rb
index c9a9eb6a16..69bf92fc58 100644
--- a/app/controllers/settings/github_syncer_controller.rb
+++ b/app/controllers/settings/github_syncer_controller.rb
@@ -28,7 +28,7 @@ def update
     render json: {
       error: {
         type: :invalid_github_solution_syncer,
-        message: syncer.errors.full_messages.to_sentence
+        message: update_error_message(syncer)
       }
     }, status: :bad_request
   end
@@ -84,4 +84,13 @@ def callback
   def destroy
     current_user.github_solution_syncer&.destroy
   end
+
+  private
+  def update_error_message(syncer)
+    if syncer.errors.of_kind?(:main_branch_name, :invalid)
+      return t(".invalid_main_branch_name", max_length: User::GithubSolutionSyncer::MAX_BRANCH_NAME_LENGTH)
+    end
+
+    t(".failed")
+  end
 end
diff --git a/config/locales/views/settings/github_syncer.yml b/config/locales/views/settings/github_syncer.yml
index 5087034194..f92e4b398e 100644
--- a/config/locales/views/settings/github_syncer.yml
+++ b/config/locales/views/settings/github_syncer.yml
@@ -4,3 +4,6 @@ en:
       show:
         github_syncer:
           heading: GitHub Syncer
+      update:
+        invalid_main_branch_name: "The main branch name must be a valid Git branch name of up to %{max_length} characters, using only letters, numbers, dots, dashes, underscores and slashes."
+        failed: "We couldn't save your GitHub Syncer settings."
diff --git a/test/controllers/settings/github_syncer_controller_test.rb b/test/controllers/settings/github_syncer_controller_test.rb
index 3fe583a345..e3825f1ba7 100644
--- a/test/controllers/settings/github_syncer_controller_test.rb
+++ b/test/controllers/settings/github_syncer_controller_test.rb
@@ -28,7 +28,9 @@ class Settings::GithubSyncerControllerTest < ActionDispatch::IntegrationTest
     assert_response :bad_request
     error = response.parsed_body["error"]
     assert_equal "invalid_github_solution_syncer", error["type"]
-    assert_equal "Main branch name is invalid", error["message"]
+    expected = "The main branch name must be a valid Git branch name of up to 100 characters, " \
+               "using only letters, numbers, dots, dashes, underscores and slashes."
+    assert_equal expected, error["message"]
 
     syncer.reload
     assert_equal "main", syncer.main_branch_name