diff --git a/src/blockchain_db/berkeleydb/db_bdb.h b/src/blockchain_db/berkeleydb/db_bdb.h
index 42119da9..aee160fa 100644
--- a/src/blockchain_db/berkeleydb/db_bdb.h
+++ b/src/blockchain_db/berkeleydb/db_bdb.h
@@ -31,6 +31,7 @@
 #include "cryptonote_protocol/blobdatatype.h" // for type blobdata
 
 #include <unordered_map>
+#include <condition_variable>
 
 // ND: Enables multi-threaded bulk reads for when getting indices.
 //     TODO: Disabled for now, as it doesn't seem to provide noticeable improvements (??. Reason: TBD.