diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 5ca0e0ae0f..3e7af11886 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -149,7 +149,7 @@ typedef SSIZE_T	ssize_t;
 #include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
 #endif
 
-#if defined(__APPLE__) || defined (BSD)
+#if defined(__APPLE__) || defined (BSD) || defined(__FreeBSD_kernel__)
 # if !(defined(MDB_USE_POSIX_MUTEX) || defined(MDB_USE_POSIX_SEM))
 # define MDB_USE_SYSV_SEM	1
 # endif