diff --git a/CHANGELOG b/CHANGELOG
index a169faba7..91f550c84 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix base URL resolving on attribute values with no quotes (#1489275)
 - Fix wrong handling of links with '|' character (#1489276)
 - Fix colorspace issue on image conversion using ImageMagick (#1489270)
 - Fix XSS vulnerability when saving HTML signatures (#1489251)
diff --git a/program/lib/Roundcube/rcube_base_replacer.php b/program/lib/Roundcube/rcube_base_replacer.php
index fcd85c2c8..aaaa2028c 100644
--- a/program/lib/Roundcube/rcube_base_replacer.php
+++ b/program/lib/Roundcube/rcube_base_replacer.php
@@ -44,8 +44,8 @@ class rcube_base_replacer
     public function replace($body)
     {
         return preg_replace_callback(array(
-            '/(src|background|href)=(["\']?)([^"\'\s]+)(\2|\s|>)/Ui',
-            '/(url\s*\()(["\']?)([^"\'\)\s]+)(\2)\)/Ui',
+            '/(src|background|href)=(["\']?)([^"\'\s>]+)(\2|\s|>)/i',
+            '/(url\s*\()(["\']?)([^"\'\)\s]+)(\2)\)/i',
         ),
         array($this, 'callback'), $body);
     }
diff --git a/tests/Framework/BaseReplacer.php b/tests/Framework/BaseReplacer.php
index e00b9e5eb..44a9604ac 100644
--- a/tests/Framework/BaseReplacer.php
+++ b/tests/Framework/BaseReplacer.php
@@ -17,4 +17,18 @@ class Framework_BaseReplacer extends PHPUnit_Framework_TestCase
 
         $this->assertInstanceOf('rcube_base_replacer', $object, "Class constructor");
     }
+
+    /**
+     * Test replace()
+     */
+    function test_replace()
+    {
+        $base = 'http://thisshouldntbetheurl.bob.com/';
+        $html = '<A href=http://shouldbethislink.com>Test URL</A>';
+
+        $replacer = new rcube_base_replacer($base);
+        $response = $replacer->replace($html);
+
+        $this->assertSame('<A href="http://shouldbethislink.com">Test URL</A>', $response);
+    }
 }