diff --git a/src/segtree.c b/src/segtree.c
index e859f84..1ba4363 100644
--- a/src/segtree.c
+++ b/src/segtree.c
@@ -1086,7 +1086,7 @@ void interval_map_decompose(struct expr *set)
 					prefix->comment = xstrdup(low->comment);
 				if (low->timeout)
 					prefix->timeout = low->timeout;
-				if (low->left->expiration)
+				if (low->expiration)
 					prefix->expiration = low->expiration;
 			}