diff --git a/hydra-module.nix b/hydra-module.nix
index 9876ca70..a250f96d 100644
--- a/hydra-module.nix
+++ b/hydra-module.nix
@@ -19,6 +19,7 @@ let
   env =
     { NIX_REMOTE = "daemon";
       SSL_CERT_FILE = "/etc/ssl/certs/ca-certificates.crt";
+      OPENSSL_X509_CERT_FILE = "/etc/ssl/certs/ca-certificates.crt"; # FIXME: remove on NixOS >= 15.07
       PGPASSFILE = "${baseDir}/pgpass";
     } // hydraEnv // cfg.extraEnv;