diff --git a/backends/functional/smtlib.cc b/backends/functional/smtlib.cc
index c496b537591..bc1253b8837 100644
--- a/backends/functional/smtlib.cc
+++ b/backends/functional/smtlib.cc
@@ -24,7 +24,7 @@ USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN
 
 const char illegal_characters[] = "#:\\";
-const char *reserved_keywords[] = {};
+const char *reserved_keywords[] = {nullptr};
 
 struct SmtScope {
   pool<std::string> used_names;