diff --git a/src/fdb5/daos/DaosArrayHandle.h b/src/fdb5/daos/DaosArrayHandle.h
index f0bc752e2..51fc835de 100644
--- a/src/fdb5/daos/DaosArrayHandle.h
+++ b/src/fdb5/daos/DaosArrayHandle.h
@@ -14,7 +14,7 @@
 #pragma once
 
 #include "eckit/io/DataHandle.h"
-
+#include <optional>
 #include "fdb5/daos/DaosSession.h"
 #include "fdb5/daos/DaosName.h"
 
diff --git a/src/fdb5/daos/DaosArrayPartHandle.h b/src/fdb5/daos/DaosArrayPartHandle.h
index e82457390..28e6b3ee7 100644
--- a/src/fdb5/daos/DaosArrayPartHandle.h
+++ b/src/fdb5/daos/DaosArrayPartHandle.h
@@ -14,7 +14,7 @@
 #pragma once
 
 #include "eckit/io/DataHandle.h"
-
+#include <optional>
 #include "fdb5/daos/DaosSession.h"
 #include "fdb5/daos/DaosName.h"
 
diff --git a/src/fdb5/daos/DaosCatalogue.h b/src/fdb5/daos/DaosCatalogue.h
index 3cfdae898..0ce743d34 100644
--- a/src/fdb5/daos/DaosCatalogue.h
+++ b/src/fdb5/daos/DaosCatalogue.h
@@ -18,6 +18,7 @@
 #include "fdb5/daos/DaosCommon.h"
 #include "fdb5/daos/DaosEngine.h"
 #include "fdb5/daos/DaosOID.h"
+#include <optional>
 
 namespace fdb5 {
 
diff --git a/src/fdb5/daos/DaosKeyValueHandle.h b/src/fdb5/daos/DaosKeyValueHandle.h
index d0193b94d..95272089e 100644
--- a/src/fdb5/daos/DaosKeyValueHandle.h
+++ b/src/fdb5/daos/DaosKeyValueHandle.h
@@ -14,7 +14,7 @@
 #pragma once
 
 #include "eckit/io/DataHandle.h"
-
+#include <optional>
 #include "fdb5/daos/DaosName.h"
 #include "fdb5/daos/DaosSession.h"