diff --git a/spec/compiler/formatter/formatter_spec.cr b/spec/compiler/formatter/formatter_spec.cr
index 7c332aac3b0a..8a44355ec67f 100644
--- a/spec/compiler/formatter/formatter_spec.cr
+++ b/spec/compiler/formatter/formatter_spec.cr
@@ -918,6 +918,13 @@ describe Crystal::Formatter do
     end
     CRYSTAL
 
+  assert_format <<-CRYSTAL
+    def foo(
+      a, b,
+    )
+    end
+    CRYSTAL
+
   assert_format <<-CRYSTAL
     macro foo(
       a,
diff --git a/src/compiler/crystal/tools/formatter.cr b/src/compiler/crystal/tools/formatter.cr
index 796afe0730de..5cc74abdca92 100644
--- a/src/compiler/crystal/tools/formatter.cr
+++ b/src/compiler/crystal/tools/formatter.cr
@@ -1651,7 +1651,7 @@ module Crystal
       yield
 
       # Write "," before skipping spaces to prevent inserting comment between argument and comma.
-      write "," if has_more || (wrote_newline && @token.type.op_comma?) || (write_trailing_comma && flag?("def_trailing_comma"))
+      write "," if has_more || (wrote_newline && @token.type.op_comma?) || (write_trailing_comma && flag?("def_trailing_comma")) || (write_trailing_comma && @token.type.op_comma?)
 
       just_wrote_newline = skip_space
       if @token.type.newline?