diff --git a/languages.toml b/languages.toml
index 105895034..9d7e4be0a 100644
--- a/languages.toml
+++ b/languages.toml
@@ -648,6 +648,7 @@ comment-token = "#"
 indent = { tab-width = 2, unit = "  " }
 grammar = "ruby"
 language-servers = [ "crystalline" ]
+formatter = { command = "crystal", args = ["tool", "format", "-"] }
 
 [[language]]
 name = "c-sharp"