diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index 890c16627aa..4bee0a0de80 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -3191,9 +3191,10 @@ function img_picto($titlealt, $picto, $moreatt = '', $pictoisfullpath = false, $
 
 	// We forge fullpathpicto for image to $path/img/$picto. By default, we take DOL_URL_ROOT/theme/$conf->theme/img/$picto
 	$url = DOL_URL_ROOT;
-	$theme = $conf->theme;
-	$path = 'theme/'.$theme;
 
+	if (isset($conf->theme)) {
+		$theme = $conf->theme;
+	}
 	// Define fullpathpicto to use into src
 	if ($pictoisfullpath) {
 		// Clean parameters