diff --git a/tenseal/tensealencoder.h b/tenseal/tensealencoder.h
index ecf98333..3552f3e2 100644
--- a/tenseal/tensealencoder.h
+++ b/tenseal/tensealencoder.h
@@ -5,6 +5,7 @@
 
 #include <any>
 #include <map>
+#include <optional>
 #include <typeindex>
 #include <vector>
 
diff --git a/tenseal/tensors/ckksvector.cpp b/tenseal/tensors/ckksvector.cpp
index cef4b042..7a504d77 100644
--- a/tenseal/tensors/ckksvector.cpp
+++ b/tenseal/tensors/ckksvector.cpp
@@ -3,6 +3,7 @@
 #include <seal/seal.h>
 
 #include <memory>
+#include <optional>
 #include <vector>
 
 #include "tenseal/tensealcontext.h"
diff --git a/tenseal/tensors/ckksvector.h b/tenseal/tensors/ckksvector.h
index cba92041..1b20cda5 100644
--- a/tenseal/tensors/ckksvector.h
+++ b/tenseal/tensors/ckksvector.h
@@ -4,6 +4,7 @@
 #include <seal/seal.h>
 
 #include <memory>
+#include <optional>
 #include <vector>
 
 #include "tenseal/tensealcontext.h"