diff --git a/r3bbase/R3BFileSource2.h b/r3bbase/R3BFileSource2.h
index 82f024a2c..cb61538dd 100644
--- a/r3bbase/R3BFileSource2.h
+++ b/r3bbase/R3BFileSource2.h
@@ -16,6 +16,7 @@
 #include "FairSource.h"
 #include "R3BShared.h"
 #include <TObjString.h>
+#include <optional>
 
 class FairRootManager;
 class TChain;
diff --git a/r3bsource/base/utils/R3BUcesbMappingFlag.h b/r3bsource/base/utils/R3BUcesbMappingFlag.h
index 6fe53da67..e06c3dec0 100644
--- a/r3bsource/base/utils/R3BUcesbMappingFlag.h
+++ b/r3bsource/base/utils/R3BUcesbMappingFlag.h
@@ -16,6 +16,7 @@
 #include <cstdint>
 #include <ext_data_client.h>
 #include <fmt/format.h>
+#include <ostream>
 
 constexpr auto UCESB_MAP_BITSIZE = 32;