diff --git a/src/Currency.php b/src/Currency.php
index e342b23..9985dd3 100644
--- a/src/Currency.php
+++ b/src/Currency.php
@@ -93,7 +93,7 @@ final public function set_alphabetic_code( $alphabetic_code ) {
 			throw new \InvalidArgumentException(
 				\sprintf(
 					'The alphabetical code of a currency must consist of 3 characters: %s.',
-					$alphabetic_code
+					\esc_html( $alphabetic_code )
 				)
 			);
 		}