diff --git a/kernel/hashlib.h b/kernel/hashlib.h
index 12349b21cfb..278832c008f 100644
--- a/kernel/hashlib.h
+++ b/kernel/hashlib.h
@@ -205,6 +205,18 @@ template<typename... T> struct hash_ops<std::variant<T...>> {
 	}
 };
 
+template<typename T> struct hash_ops<std::optional<T>> {
+	static inline bool cmp(std::optional<T> a, std::optional<T> b) {
+		return a == b;
+	}
+	static inline unsigned int hash(std::optional<T> a) {
+		if(a.has_value())
+			return mkhash(*a);
+		else
+			return 0;
+	}
+};
+
 inline int hashtable_size(int min_size)
 {
 	static std::vector<int> zero_and_some_primes = {
diff --git a/kernel/yosys_common.h b/kernel/yosys_common.h
index 4391ad582ee..86d448d211b 100644
--- a/kernel/yosys_common.h
+++ b/kernel/yosys_common.h
@@ -31,6 +31,7 @@
 #include <unordered_set>
 #include <initializer_list>
 #include <variant>
+#include <optional>
 #include <stdexcept>
 #include <memory>
 #include <cmath>