diff --git a/papaparse.js b/papaparse.js
index 193af60..0bf25bd 100755
--- a/papaparse.js
+++ b/papaparse.js
@@ -326,7 +326,7 @@
 				return;
 
 			if (typeof _config.delimiter === 'string'
-                && !Papa.BAD_DELIMITERS.filter(function(value) { return _config.delimiter.includes(value); }).length)
+                && !Papa.BAD_DELIMITERS.filter(function(value) { return _config.delimiter.indexOf(value) !== -1; }).length)
 			{
 				// We have a string as config and it does not contains any
 				// of the invalid delimiters.