problem with encoding

Encoding::CompatibilityError (incompatible character encodings: ASCII-8BIT and UTF-8): app/views/projects/commits/show.html.haml:21:in _app_views_projects_commits_show_html_haml___1553931052578523260_69841100314240' app/controllers/projects/commits_controller.rb:18:in show'

Completed 500 Internal Server Error in 437ms (Views: 36.5ms | ActiveRecord: 17.0ms)

Encoding::CompatibilityError (incompatible character encodings: ASCII-8BIT and UTF-8): app/views/projects/tree/show.html.haml:10:in _app_views_projects_tree_show_html_haml___4058792367249074794_69841106443900' app/controllers/projects/tree_controller.rb:13:in show'

Completed 500 Internal Server Error in 48ms (Views: 8.6ms | ActiveRecord: 3.3ms)