diff --git a/src/wp-includes/default-constants.php b/src/wp-includes/default-constants.php
index 79e16428ed13b..f1c0320a6fc27 100644
--- a/src/wp-includes/default-constants.php
+++ b/src/wp-includes/default-constants.php
@@ -58,6 +58,8 @@ function wp_initial_constants() {
 			define( 'WP_MAX_MEMORY_LIMIT', $current_limit );
 		} elseif ( -1 === $current_limit_int || $current_limit_int > 268435456 /* = 256M */ ) {
 			define( 'WP_MAX_MEMORY_LIMIT', $current_limit );
+		} elseif ( wp_convert_hr_to_bytes( WP_MEMORY_LIMIT ) > 268435456 /* = 256M */ ) {
+			define( 'WP_MAX_MEMORY_LIMIT', WP_MEMORY_LIMIT );
 		} else {
 			define( 'WP_MAX_MEMORY_LIMIT', '256M' );
 		}