diff --git a/util/models.c b/util/models.c
index 48e58f4f1c..0d54a456bf 100644
--- a/util/models.c
+++ b/util/models.c
@@ -94,3 +94,16 @@ void isc__mempool_put(void *mem, void *ptr FLARG) {
 	if (!mem) __coverity_panic__();
 	__coverity_free__(ptr);
 }
+
+/*
+ * Cmocka models.
+ */
+
+#define LargestIntegralType unsigned long int
+
+void _assert_true(const LargestIntegralType result,
+		  const char * const expression,
+		  const char * const file, const int line)
+{
+	if (!result) __coverity_panic__();
+}