diff --git a/pkgs/servers/mail/postfix/default.nix b/pkgs/servers/mail/postfix/default.nix
index 41dfebab7907..d88b9f8b0dbc 100644
--- a/pkgs/servers/mail/postfix/default.nix
+++ b/pkgs/servers/mail/postfix/default.nix
@@ -13,7 +13,7 @@ let
    ] ++ lib.optional withPgSQL "-DHAS_PGSQL"
      ++ lib.optionals withMySQL [ "-DHAS_MYSQL" "-I${mysql.connector-c}/include/mysql" "-L${mysql.connector-c}/lib/mysql" ]
      ++ lib.optional withSQLite "-DHAS_SQLITE"
-     ++ lib.optional withLDAP "-DHAS_LDAP");
+     ++ lib.optionals withLDAP ["-DHAS_LDAP" "-DUSE_LDAP_SASL"]);
    auxlibs = lib.concatStringsSep " " ([
      "-ldb" "-lnsl" "-lresolv" "-lsasl2" "-lcrypto" "-lssl"
    ] ++ lib.optional withPgSQL "-lpq"