diff --git a/gcc/testsuite/gcc.dg/vect/tree-vect.h b/gcc/testsuite/gcc.dg/vect/tree-vect.h
index 69c93ac8092b105164a915865a7538c1956dd4df..5d8d9eba3f8e90a922daf71415f76c1116332f63 100644
--- a/gcc/testsuite/gcc.dg/vect/tree-vect.h
+++ b/gcc/testsuite/gcc.dg/vect/tree-vect.h
@@ -85,3 +85,9 @@ check_vect (void)
 #else
 #  define VECTOR_BITS 128
 #endif
+
+/* Which most of our tests are going to #define for internal use, and
+   which might be exposed by system headers related to signal.h on some
+   targets, notably VxWorks.  */
+#undef OFFSET
+