diff --git a/qm-plugins/qm-alloptions/class-qm-collector-alloptions.php b/qm-plugins/qm-alloptions/class-qm-collector-alloptions.php
index 9d77c2baa8..93595c1367 100644
--- a/qm-plugins/qm-alloptions/class-qm-collector-alloptions.php
+++ b/qm-plugins/qm-alloptions/class-qm-collector-alloptions.php
@@ -24,7 +24,7 @@ public function process() {
 		$options    = [];
 
 		foreach ( $alloptions as $name => $val ) {
-			$size        = mb_strlen( $val );
+			$size        = is_null( $val ) ? 0 : mb_strlen( $val );
 			$total_size += $size;
 
 			$option = new stdClass();