diff --git a/tests/test-runner.h b/tests/test-runner.h
index 238e6134..253df818 100644
--- a/tests/test-runner.h
+++ b/tests/test-runner.h
@@ -1,6 +1,10 @@
 #ifndef _TEST_RUNNER_H_
 #define _TEST_RUNNER_H_
 
+#ifdef NDEBUG
+#error "Tests must not be built with NDEBUG defined, they rely on assert()."
+#endif
+
 struct test {
 	const char *name;
 	void (*run)(void);