diff --git a/src/test/run-pass/issue-2723-b.rs b/src/test/run-pass/issue-2723-b.rs
index 895a0df19e70..4c5c9ca1d207 100644
--- a/src/test/run-pass/issue-2723-b.rs
+++ b/src/test/run-pass/issue-2723-b.rs
@@ -1,3 +1,4 @@
+// xfail-fast: aux-build not compatible with fast
 // aux-build:issue_2723_a.rs
 
 use issue_2723_a;