diff --git a/docs/_docs/configuration/default.md b/docs/_docs/configuration/default.md
index 68ab49fc9bd..f87f71e3e7e 100644
--- a/docs/_docs/configuration/default.md
+++ b/docs/_docs/configuration/default.md
@@ -79,7 +79,7 @@ redcarpet:
 kramdown:
   auto_ids          : true
   entity_output     : as_char
-  toc_levels        : 1..6
+  toc_levels        : [1, 2, 3, 4, 5, 6]
   smart_quotes      : lsquo,rsquo,ldquo,rdquo
   input             : GFM
   hard_wrap         : false
diff --git a/lib/jekyll/configuration.rb b/lib/jekyll/configuration.rb
index 298a90fa932..9e86a560c85 100644
--- a/lib/jekyll/configuration.rb
+++ b/lib/jekyll/configuration.rb
@@ -66,7 +66,7 @@ class Configuration < Hash
 
       "kramdown"            => {
         "auto_ids"      => true,
-        "toc_levels"    => "1..6",
+        "toc_levels"    => (1..6).to_a,
         "entity_output" => "as_char",
         "smart_quotes"  => "lsquo,rsquo,ldquo,rdquo",
         "input"         => "GFM",