diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 9c1dd91183..1cec612013 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -135,6 +135,9 @@ typedef SSIZE_T	ssize_t;
 # endif
 #elif defined(ANDROID)
 # define MDB_FDATASYNC		fsync
+#elif defined(__HAIKU__)
+# define MDB_USE_POSIX_SEM	1
+# define MDB_FDATASYNC		fsync
 #endif
 
 /* NetBSD does not define union semun in sys/sem.h */