diff --git a/src/Symfony/Component/DomCrawler/Crawler.php b/src/Symfony/Component/DomCrawler/Crawler.php
index f51c56a302264..e8f6c8d8116ca 100644
--- a/src/Symfony/Component/DomCrawler/Crawler.php
+++ b/src/Symfony/Component/DomCrawler/Crawler.php
@@ -1027,7 +1027,7 @@ private function discoverNamespace(\DOMXPath $domxpath, $prefix)
      */
     private function findNamespacePrefixes($xpath)
     {
-        if (preg_match_all('/(?P<prefix>[a-z_][a-z_0-9\-\.]*):[^"\/]/i', $xpath, $matches)) {
+        if (preg_match_all('/(?P<prefix>[a-z_][a-z_0-9\-\.]*):[^"\/:]/i', $xpath, $matches)) {
             return array_unique($matches['prefix']);
         }