diff --git a/course/lib.php b/course/lib.php
index f9c50d3280f..6ed5bb5f0b2 100644
--- a/course/lib.php
+++ b/course/lib.php
@@ -959,7 +959,9 @@ function get_array_of_activities($courseid) {
                                    $mod[$seq]->extraclasses = $info->extraclasses;
                                }
                                if (!empty($info->iconurl)) {
-                                   $mod[$seq]->iconurl = $info->iconurl;
+                                   // Convert URL to string as it's easier to store. Also serialized object contains \0 byte and can not be written to Postgres DB.
+                                   $url = new moodle_url($info->iconurl);
+                                   $mod[$seq]->iconurl = $url->out(false);
                                }
                                if (!empty($info->onclick)) {
                                    $mod[$seq]->onclick = $info->onclick;
diff --git a/lib/modinfolib.php b/lib/modinfolib.php
index d48504ec640..8772b9ad59d 100644
--- a/lib/modinfolib.php
+++ b/lib/modinfolib.php
@@ -1079,7 +1079,8 @@ class cm_info extends stdClass {
         $this->indent           = isset($mod->indent) ? $mod->indent : 0;
         $this->extra            = isset($mod->extra) ? $mod->extra : '';
         $this->extraclasses     = isset($mod->extraclasses) ? $mod->extraclasses : '';
-        $this->iconurl          = isset($mod->iconurl) ? $mod->iconurl : '';
+        // iconurl may be stored as either string or instance of moodle_url.
+        $this->iconurl          = isset($mod->iconurl) ? new moodle_url($mod->iconurl) : '';
         $this->onclick          = isset($mod->onclick) ? $mod->onclick : '';
         $this->content          = isset($mod->content) ? $mod->content : '';
         $this->icon             = isset($mod->icon) ? $mod->icon : '';