diff --git a/lib/liquid/variable_lookup.rb b/lib/liquid/variable_lookup.rb
index 06c24b764..340c0b66d 100644
--- a/lib/liquid/variable_lookup.rb
+++ b/lib/liquid/variable_lookup.rb
@@ -6,7 +6,7 @@ class VariableLookup
 
     attr_reader :name, :lookups
 
-    def self.parse(markup, string_scanner, cache = nil)
+    def self.parse(markup, string_scanner = StringScanner.new(""), cache = nil)
       new(markup, string_scanner, cache)
     end
 
diff --git a/lib/liquid/version.rb b/lib/liquid/version.rb
index 4cfca9b16..0cc2adc85 100644
--- a/lib/liquid/version.rb
+++ b/lib/liquid/version.rb
@@ -2,5 +2,5 @@
 # frozen_string_literal: true
 
 module Liquid
-  VERSION = "5.6.3"
+  VERSION = "5.6.4"
 end