diff --git a/assert/tst-assert-c++.cc b/assert/tst-assert-c++.cc
index 41cb487512..a175f5e961 100644
--- a/assert/tst-assert-c++.cc
+++ b/assert/tst-assert-c++.cc
@@ -16,6 +16,9 @@
License along with the GNU C Library; if not, see
. */
+/* We do not want the compiler or any other pre-included header from
+ removing the assert we want to test, so undefine NDEBUG right now. */
+#undef NDEBUG
#include
/* The C++ standard requires that if the assert argument is a constant