diff --git a/array.c b/array.c
index f8faf697bf..0700a03193 100644
--- a/array.c
+++ b/array.c
@@ -2008,6 +2008,7 @@ ary_join_1(VALUE obj, VALUE ary, VALUE sep, long i, VALUE result, int *first)
 	    else {
 		VALUE args[4];
 
+		*first = FALSE;
 		args[0] = val;
 		args[1] = sep;
 		args[2] = result;