diff --git a/servers/slapd/back-bdb/index.c b/servers/slapd/back-bdb/index.c
index 9059b9a4d2..c45e07a8b9 100644
--- a/servers/slapd/back-bdb/index.c
+++ b/servers/slapd/back-bdb/index.c
@@ -20,6 +20,7 @@
 
 #include <ac/string.h>
 #include <ac/socket.h>
+#include <ac/errno.h>
 
 #include "slap.h"
 #include "back-bdb.h"