diff --git a/libcxxabi/test/cxa_vec_new_overflow_PR41395.pass.cpp b/libcxxabi/test/cxa_vec_new_overflow_PR41395.pass.cpp
--- a/libcxxabi/test/cxa_vec_new_overflow_PR41395.pass.cpp
+++ b/libcxxabi/test/cxa_vec_new_overflow_PR41395.pass.cpp
@@ -18,7 +18,7 @@
 void dummy_ctor(void*) { assert(false && "should not be called"); }
 void dummy_dtor(void*) { assert(false && "should not be called"); }
 
-void *dummy_alloc(size_t) { assert(false && "should not be called"); }
+void *dummy_alloc(size_t) { assert(false && "should not be called"); __builtin_unreachable(); }
 void dummy_dealloc(void*) { assert(false && "should not be called"); }
 void dummy_dealloc_sized(void*, size_t) { assert(false && "should not be called"); }