diff --git a/tests/coverage.h b/tests/coverage.h
index 3d0755e3..04345793 100644
--- a/tests/coverage.h
+++ b/tests/coverage.h
@@ -58,6 +58,7 @@
 #undef BUFFERI_CONTRACT
 #undef ILISTI_CONTRACT
 #undef DEQUEI_CONTRACT
+#undef NDEBUG
 #else
 /* For normal builds, empty macros which does nothing */
 #define START_COVERAGE