diff --git a/third_party/exprtk/exprtk.hpp b/third_party/exprtk/exprtk.hpp
index 1848dddfc441..8a755e3c50b5 100644
--- a/third_party/exprtk/exprtk.hpp
+++ b/third_party/exprtk/exprtk.hpp
@@ -21302,7 +21302,7 @@ namespace exprtk
       inline bool valid() const
       {
          // Symbol table sanity check.
-         return control_block_ && control_block_->data_;
+         return (control_block_ != nullptr) && (control_block_->data_ != nullptr);
       }
 
       inline void load_from(const symbol_table<T>& st)