diff --git a/papaparse.js b/papaparse.js
index 618d58d..3b3aa32 100644
--- a/papaparse.js
+++ b/papaparse.js
@@ -608,6 +608,9 @@
 		function getFileSize(xhr)
 		{
 			var contentRange = xhr.getResponseHeader('Content-Range');
+			if (contentRange === null) { // no content range, then finish!
+        			return -1;
+            		} 
 			return parseInt(contentRange.substr(contentRange.lastIndexOf('/') + 1));
 		}
 	}