diff --git a/snakefmt/formatter.py b/snakefmt/formatter.py
index 65e2bf5..9febbfe 100644
--- a/snakefmt/formatter.py
+++ b/snakefmt/formatter.py
@@ -351,7 +351,7 @@ def format_param(
             for comment in parameter.pre_comments:
                 result += f"{string_indent}{comment}\n"
         result += val.strip("\n")
-        if param_list:
+        if param_list and len(val) > 1:
             result += ","
         post_comment_iter = iter(parameter.post_comments)
         if parameter._has_inline_comment: