diff --git wp-includes/meta.php wp-includes/meta.php
index a318bbe..c575d31 100644
--- wp-includes/meta.php
+++ wp-includes/meta.php
@@ -748,6 +748,7 @@ class WP_Meta_Query {
 					$meta_value = preg_split( '/[,\s]+/', $meta_value );
 
 				if ( empty( $meta_value ) ) {
+					_doing_it_wrong( 'meta query', sprintf( __( "When operator is set to '%s', the meta value is expected to be an array with at least one element." ), $meta_compare ) );
 					unset( $join[$i] );
 					continue;
 				}