diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index d4a2996be0..3daa69b1e9 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -166,7 +166,7 @@ typedef SSIZE_T	ssize_t;
 # define MDB_USE_ROBUST	1
 #elif defined(__APPLE__) || defined (BSD) || defined(__FreeBSD_kernel__)
 # if defined(__APPLE__) && !defined(MDB_USE_ROBUST)
-# define MSB_USE_POSIX_SEM	1
+# define MDB_USE_POSIX_SEM	1
 # endif
 # if !(defined(MDB_USE_POSIX_MUTEX) || defined(MDB_USE_POSIX_SEM))
 # define MDB_USE_SYSV_SEM	1