diff --git a/lib/liquid/standardfilters.rb b/lib/liquid/standardfilters.rb
index 50f2dc4..c87cd7c 100644
--- a/lib/liquid/standardfilters.rb
+++ b/lib/liquid/standardfilters.rb
@@ -65,9 +65,10 @@ module Liquid
       return if input.nil?
       input_str = input.to_s
       length = Utils.to_integer(length)
-      l = length - truncate_string.length
+      truncate_string_str = truncate_string.to_s
+      l = length - truncate_string_str.length
       l = 0 if l < 0
-      input_str.length > length ? input_str[0...l] + truncate_string : input_str
+      input_str.length > length ? input_str[0...l] + truncate_string_str : input_str
     end
 
     def truncatewords(input, words = 15, truncate_string = "...".freeze)
diff --git a/test/integration/standard_filter_test.rb b/test/integration/standard_filter_test.rb
index 909ad44..c852ac6 100644
--- a/test/integration/standard_filter_test.rb
+++ b/test/integration/standard_filter_test.rb
@@ -115,6 +115,7 @@ class StandardFiltersTest < Minitest::Test
     assert_equal '...', @filters.truncate('1234567890', 0)
     assert_equal '1234567890', @filters.truncate('1234567890')
     assert_equal "测试...", @filters.truncate("测试测试测试测试", 5)
+    assert_equal '12341', @filters.truncate("1234567890", 5, 1)
   end
 
   def test_split