diff --git a/src/Image.php b/src/Image.php
index 05b0056..040c59f 100644
--- a/src/Image.php
+++ b/src/Image.php
@@ -373,6 +373,8 @@ public function isExcluded( $string, $excluded_values ) {
 			$excluded_values = (array) $excluded_values;
 		}
 
+		$excluded_values = array_filter( $excluded_values );
+
 		if ( empty( $excluded_values ) ) {
 			return false;
 		}