diff --git a/mod/url/db/install.xml b/mod/url/db/install.xml
index eb8f4d2f4c1..d042027dd7c 100644
--- a/mod/url/db/install.xml
+++ b/mod/url/db/install.xml
@@ -11,7 +11,7 @@
         <FIELD NAME="name" TYPE="char" LENGTH="255" NOTNULL="true" SEQUENCE="false" PREVIOUS="course" NEXT="intro"/>
         <FIELD NAME="intro" TYPE="text" LENGTH="small" NOTNULL="false" SEQUENCE="false" PREVIOUS="name" NEXT="introformat"/>
         <FIELD NAME="introformat" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" PREVIOUS="intro" NEXT="externalurl"/>
-        <FIELD NAME="externalurl" TYPE="text" LENGTH="small" NOTNULL="false" SEQUENCE="false" PREVIOUS="introformat" NEXT="display"/>
+        <FIELD NAME="externalurl" TYPE="text" LENGTH="small" NOTNULL="true" SEQUENCE="false" PREVIOUS="introformat" NEXT="display"/>
         <FIELD NAME="display" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" DEFAULT="0" SEQUENCE="false" PREVIOUS="externalurl" NEXT="displayoptions"/>
         <FIELD NAME="displayoptions" TYPE="text" LENGTH="small" NOTNULL="false" SEQUENCE="false" PREVIOUS="display" NEXT="parameters"/>
         <FIELD NAME="parameters" TYPE="text" LENGTH="small" NOTNULL="false" SEQUENCE="false" PREVIOUS="displayoptions" NEXT="timemodified"/>
diff --git a/mod/url/db/upgrade.php b/mod/url/db/upgrade.php
index 8c995bfae49..01926f80c9c 100644
--- a/mod/url/db/upgrade.php
+++ b/mod/url/db/upgrade.php
@@ -53,6 +53,20 @@ function xmldb_url_upgrade($oldversion) {
 
     // Moodle v2.1.0 release upgrade line
     // Put any upgrade step following this
+    if ($oldversion < 2011092800) {
+
+        // Changing nullability of field externalurl on table urls to not-null
+        $table = new xmldb_table('url');
+        $field = new xmldb_field('externalurl', XMLDB_TYPE_TEXT, 'small', null,
+                XMLDB_NOTNULL, null, null, 'introformat');
+
+        $DB->set_field_select('url', 'externalurl', $DB->sql_empty(), 'externalurl IS NULL');
+        // Launch change of nullability for field =externalurl
+        $dbman->change_field_notnull($table, $field);
+
+        // url savepoint reached
+        upgrade_mod_savepoint(true, 2011092800, 'url');
+    }
 
     return true;
 }
diff --git a/mod/url/lang/en/url.php b/mod/url/lang/en/url.php
index be6867d4743..4498394bc59 100644
--- a/mod/url/lang/en/url.php
+++ b/mod/url/lang/en/url.php
@@ -45,6 +45,7 @@ $string['displayselectexplain'] = 'Choose display type, unfortunately not all ty
 $string['externalurl'] = 'External URL';
 $string['framesize'] = 'Frame height';
 $string['chooseavariable'] = 'Choose a variable...';
+$string['invalidurl'] = 'Entered URL is invalid';
 $string['modulename'] = 'URL';
 $string['modulenameplural'] = 'URLs';
 $string['neverseen'] = 'Never seen';
diff --git a/mod/url/mod_form.php b/mod/url/mod_form.php
index da6a7209dc7..790b85dc534 100644
--- a/mod/url/mod_form.php
+++ b/mod/url/mod_form.php
@@ -50,6 +50,7 @@ class mod_url_mod_form extends moodleform_mod {
         //-------------------------------------------------------
         $mform->addElement('header', 'content', get_string('contentheader', 'url'));
         $mform->addElement('url', 'externalurl', get_string('externalurl', 'url'), array('size'=>'60'), array('usefilepicker'=>true));
+        $mform->addRule('externalurl', null, 'required', null, 'client');
         //-------------------------------------------------------
         $mform->addElement('header', 'optionssection', get_string('optionsheader', 'url'));
 
@@ -165,4 +166,14 @@ class mod_url_mod_form extends moodleform_mod {
         }
     }
 
+    function validation($data, $files) {
+        $errors = parent::validation($data, $files);
+        //Validating Entered url
+        $data['externalurl'] = clean_param($data['externalurl'], PARAM_URL);
+        if (empty($data['externalurl'])) {
+            $errors['externalurl'] = get_string('invalidurl', 'url');
+        }
+        return $errors;
+    }
+
 }
diff --git a/mod/url/version.php b/mod/url/version.php
index 5b4c1b54024..a769049edc9 100644
--- a/mod/url/version.php
+++ b/mod/url/version.php
@@ -26,7 +26,7 @@
 
 defined('MOODLE_INTERNAL') || die;
 
-$module->version  = 2010101400;
+$module->version  = 2011092800;
 $module->requires = 2010080300;  // Requires this Moodle version
 $module->cron     = 0;