diff --git a/api/src/Html/HtmLawed.php b/api/src/Html/HtmLawed.php
index 2e80f30a7f..a66e02d120 100644
--- a/api/src/Html/HtmLawed.php
+++ b/api/src/Html/HtmLawed.php
@@ -164,7 +164,7 @@ class HtmLawed
 		$style = $style2buffer ?? '';
 		// clean out comments and stuff
 		$search = array(
-			'@url\(http:\/\/[^\)].*?\)@si',  // url calls e.g. in style definitions
+			'@url\(https?:\/\/[^\)].*?\)@si',  // url calls e.g. in style definitions
 //			'@<!--[\s\S]*?[ \t\n\r]*-->@',   // Strip multi-line comments including CDATA
 //			'@<!--[\s\S]*?[ \t\n\r]*--@',    // Strip broken multi-line comments including CDATA
 		);