diff --git a/src/viewer.js b/src/viewer.js
index 02556bcf..92f0bb80 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -2121,9 +2121,11 @@ function getTileSourceImplementation( viewer, tileSource, imgOptions, successCal
 
     //allow plain xml strings or json strings to be parsed here
     if ( $.type( tileSource ) == 'string' ) {
-        if ( tileSource.match( /\s*<.*/ ) ) {
+        //xml should start with "<" and end with ">"
+        if ( tileSource.match( /^\s*<.*>\s*$/ ) ) {
             tileSource = $.parseXml( tileSource );
-        } else if ( tileSource.match( /\s*[\{\[].*/ ) ) {
+        //json should start with "{" or "[" and end with "}" or "]"
+        } else if ( tileSource.match(/^\s*[\{\[].*[\}\]]\s*$/ ) ) {
             tileSource = $.parseJSON(tileSource);
         }
     }