diff --git a/acmed/src/acme_proto.rs b/acmed/src/acme_proto.rs
index c755e51..20274fc 100644
--- a/acmed/src/acme_proto.rs
+++ b/acmed/src/acme_proto.rs
@@ -66,7 +66,7 @@ macro_rules! set_empty_data_builder {
     };
 }
 
-pub fn request_certificate(cert: &Certificate) -> Result<(), Error> {
+pub fn request_certificate(cert: &Certificate, root_certs: &[String]) -> Result<(), Error> {
     let domains = cert
         .domains
         .iter()
@@ -75,26 +75,26 @@ pub fn request_certificate(cert: &Certificate) -> Result<(), Error> {
     let mut hook_datas = vec![];
 
     // 1. Get the directory
-    let directory = http::get_directory(&cert.remote_url)?;
+    let directory = http::get_directory(root_certs, &cert.remote_url)?;
 
     // 2. Get a first nonce
-    let nonce = http::get_nonce(&directory.new_nonce)?;
+    let nonce = http::get_nonce(root_certs, &directory.new_nonce)?;
 
     // 3. Get or create the account
-    let (account, nonce) = AccountManager::new(cert, &directory, &nonce)?;
+    let (account, nonce) = AccountManager::new(cert, &directory, &nonce, root_certs)?;
 
     // 4. Create a new order
     let new_order = NewOrder::new(&domains);
     let new_order = serde_json::to_string(&new_order)?;
     let data_builder = set_data_builder!(account, new_order.as_bytes(), directory.new_order);
     let (order, order_url, mut nonce): (Order, String, String) =
-        http::get_obj_loc(&directory.new_order, &data_builder, &nonce)?;
+        http::get_obj_loc(root_certs, &directory.new_order, &data_builder, &nonce)?;
 
     // 5. Get all the required authorizations
     for auth_url in order.authorizations.iter() {
         let data_builder = set_empty_data_builder!(account, auth_url);
         let (auth, new_nonce): (Authorization, String) =
-            http::get_obj(&auth_url, &data_builder, &nonce)?;
+            http::get_obj(root_certs, &auth_url, &data_builder, &nonce)?;
         nonce = new_nonce;
 
         if auth.status == AuthorizationStatus::Valid {
@@ -123,7 +123,7 @@ pub fn request_certificate(cert: &Certificate) -> Result<(), Error> {
                 // 8. Tell the server the challenge has been completed
                 let chall_url = challenge.get_url();
                 let data_builder = set_data_builder!(account, b"{}", chall_url);
-                let new_nonce = http::post_challenge_response(&chall_url, &data_builder, &nonce)?;
+                let new_nonce = http::post_challenge_response(root_certs, &chall_url, &data_builder, &nonce)?;
                 nonce = new_nonce;
             }
         }
@@ -132,7 +132,7 @@ pub fn request_certificate(cert: &Certificate) -> Result<(), Error> {
         let data_builder = set_empty_data_builder!(account, auth_url);
         let break_fn = |a: &Authorization| a.status == AuthorizationStatus::Valid;
         let (_, new_nonce): (Authorization, String) =
-            http::pool_obj(&auth_url, &data_builder, &break_fn, &nonce)?;
+            http::pool_obj(root_certs, &auth_url, &data_builder, &break_fn, &nonce)?;
         nonce = new_nonce;
     }
 
@@ -140,26 +140,26 @@ pub fn request_certificate(cert: &Certificate) -> Result<(), Error> {
     let data_builder = set_empty_data_builder!(account, order_url);
     let break_fn = |o: &Order| o.status == OrderStatus::Ready;
     let (order, nonce): (Order, String) =
-        http::pool_obj(&order_url, &data_builder, &break_fn, &nonce)?;
+        http::pool_obj(root_certs, &order_url, &data_builder, &break_fn, &nonce)?;
 
     // 11. Finalize the order by sending the CSR
     let (priv_key, pub_key) = certificate::get_key_pair(cert)?;
     let csr = certificate::generate_csr(cert, &priv_key, &pub_key)?;
     let data_builder = set_data_builder!(account, csr.as_bytes(), order.finalize);
-    let (_, nonce): (Order, String) = http::get_obj(&order.finalize, &data_builder, &nonce)?;
+    let (_, nonce): (Order, String) = http::get_obj(root_certs, &order.finalize, &data_builder, &nonce)?;
 
     // 12. Pool the order in order to see whether or not it is valid
     let data_builder = set_empty_data_builder!(account, order_url);
     let break_fn = |o: &Order| o.status == OrderStatus::Valid;
     let (order, nonce): (Order, String) =
-        http::pool_obj(&order_url, &data_builder, &break_fn, &nonce)?;
+        http::pool_obj(root_certs, &order_url, &data_builder, &break_fn, &nonce)?;
 
     // 13. Download the certificate
     let crt_url = order
         .certificate
         .ok_or_else(|| Error::from("No certificate available for download."))?;
     let data_builder = set_empty_data_builder!(account, crt_url);
-    let (crt, _) = http::get_certificate(&crt_url, &data_builder, &nonce)?;
+    let (crt, _) = http::get_certificate(root_certs, &crt_url, &data_builder, &nonce)?;
     storage::write_certificate(cert, &crt.as_bytes())?;
 
     for (data, hook_type) in hook_datas.iter() {
diff --git a/acmed/src/acme_proto/account.rs b/acmed/src/acme_proto/account.rs
index 3011f74..8ea5449 100644
--- a/acmed/src/acme_proto/account.rs
+++ b/acmed/src/acme_proto/account.rs
@@ -20,6 +20,7 @@ impl AccountManager {
         cert: &Certificate,
         directory: &Directory,
         nonce: &str,
+        root_certs: &[String],
     ) -> Result<(Self, String), Error> {
         // TODO: store the key id (account url)
         let (priv_key, pub_key) = if storage::account_files_exists(cert) {
@@ -42,7 +43,7 @@ impl AccountManager {
         let data_builder =
             |n: &str| encode_jwk(&priv_key, account.as_bytes(), &directory.new_account, n);
         let (acc_rep, account_url, nonce): (AccountResponse, String, String) =
-            http::get_obj_loc(&directory.new_account, &data_builder, &nonce)?;
+            http::get_obj_loc(root_certs, &directory.new_account, &data_builder, &nonce)?;
         let ac = AccountManager {
             priv_key,
             pub_key,
diff --git a/acmed/src/acme_proto/http.rs b/acmed/src/acme_proto/http.rs
index d0ca4de..aa67fba 100644
--- a/acmed/src/acme_proto/http.rs
+++ b/acmed/src/acme_proto/http.rs
@@ -6,6 +6,7 @@ use http_req::uri::Uri;
 use log::{debug, trace, warn};
 use std::str::FromStr;
 use std::{thread, time};
+use std::path::Path;
 
 const CONTENT_TYPE_JOSE: &str = "application/jose+json";
 const CONTENT_TYPE_JSON: &str = "application/json";
@@ -24,7 +25,7 @@ impl FromStr for DummyString {
     }
 }
 
-fn new_request(uri: &Uri, method: Method) -> Request {
+fn new_request<'a>(root_certs: &'a [String], uri: &'a Uri, method: Method) -> Request<'a> {
     debug!("{}: {}", method, uri);
     let useragent = format!(
         "{}/{} ({}) {}",
@@ -34,6 +35,9 @@ fn new_request(uri: &Uri, method: Method) -> Request {
         env!("ACMED_HTTP_LIB_AGENT")
     );
     let mut rb = Request::new(uri);
+    for file_name in root_certs.iter() {
+        rb.root_cert_file_pem(&Path::new(file_name));
+    }
     rb.method(method);
     rb.header("User-Agent", &useragent);
     // TODO: allow to configure the language
@@ -93,9 +97,9 @@ fn nonce_from_response(res: &Response) -> Result<String, Error> {
     }
 }
 
-fn post_jose_type(url: &str, data: &[u8], accept_type: &str) -> Result<(Response, String), Error> {
+fn post_jose_type(root_certs: &[String], url: &str, data: &[u8], accept_type: &str) -> Result<(Response, String), Error> {
     let uri = url.parse::<Uri>()?;
-    let mut request = new_request(&uri, Method::POST);
+    let mut request = new_request(root_certs, &uri, Method::POST);
     request.header("Content-Type", CONTENT_TYPE_JOSE);
     request.header("Content-Length", &data.len().to_string());
     request.header("Accept", accept_type);
@@ -116,6 +120,7 @@ fn check_response(res: &Response, body: &str) -> Result<(), AcmeError> {
 }
 
 fn fetch_obj_type<T, G>(
+    root_certs: &[String],
     url: &str,
     data_builder: &G,
     nonce: &str,
@@ -128,7 +133,7 @@ where
     let mut nonce = nonce.to_string();
     for _ in 0..crate::DEFAULT_HTTP_FAIL_NB_RETRY {
         let data = data_builder(&nonce)?;
-        let (res, res_body) = post_jose_type(url, data.as_bytes(), accept_type)?;
+        let (res, res_body) = post_jose_type(root_certs, url, data.as_bytes(), accept_type)?;
         nonce = nonce_from_response(&res)?;
 
         match check_response(&res, &res_body) {
@@ -150,15 +155,16 @@ where
     Err("Too much errors, will not retry".into())
 }
 
-fn fetch_obj<T, G>(url: &str, data_builder: &G, nonce: &str) -> Result<(T, String, String), Error>
+fn fetch_obj<T, G>(root_certs: &[String], url: &str, data_builder: &G, nonce: &str) -> Result<(T, String, String), Error>
 where
     T: std::str::FromStr<Err = Error>,
     G: Fn(&str) -> Result<String, Error>,
 {
-    fetch_obj_type(url, data_builder, nonce, CONTENT_TYPE_JSON)
+    fetch_obj_type(root_certs, url, data_builder, nonce, CONTENT_TYPE_JSON)
 }
 
 pub fn get_obj_loc<T, G>(
+    root_certs: &[String],
     url: &str,
     data_builder: &G,
     nonce: &str,
@@ -167,7 +173,7 @@ where
     T: std::str::FromStr<Err = Error>,
     G: Fn(&str) -> Result<String, Error>,
 {
-    let (obj, location, nonce) = fetch_obj(url, data_builder, nonce)?;
+    let (obj, location, nonce) = fetch_obj(root_certs, url, data_builder, nonce)?;
     if location.is_empty() {
         Err("Location header not found.".into())
     } else {
@@ -175,16 +181,17 @@ where
     }
 }
 
-pub fn get_obj<T, G>(url: &str, data_builder: &G, nonce: &str) -> Result<(T, String), Error>
+pub fn get_obj<T, G>(root_certs: &[String], url: &str, data_builder: &G, nonce: &str) -> Result<(T, String), Error>
 where
     T: std::str::FromStr<Err = Error>,
     G: Fn(&str) -> Result<String, Error>,
 {
-    let (obj, _, nonce) = fetch_obj(url, data_builder, nonce)?;
+    let (obj, _, nonce) = fetch_obj(root_certs, url, data_builder, nonce)?;
     Ok((obj, nonce))
 }
 
 pub fn pool_obj<T, G, S>(
+    root_certs: &[String],
     url: &str,
     data_builder: &G,
     break_fn: &S,
@@ -198,7 +205,7 @@ where
     let mut nonce: String = nonce.to_string();
     for _ in 0..crate::DEFAULT_POOL_NB_TRIES {
         thread::sleep(time::Duration::from_secs(crate::DEFAULT_POOL_WAIT_SEC));
-        let (obj, _, new_nonce) = fetch_obj(url, data_builder, &nonce)?;
+        let (obj, _, new_nonce) = fetch_obj(root_certs, url, data_builder, &nonce)?;
         if break_fn(&obj) {
             return Ok((obj, new_nonce));
         }
@@ -208,15 +215,16 @@ where
     Err(msg.into())
 }
 
-pub fn post_challenge_response<G>(url: &str, data_builder: &G, nonce: &str) -> Result<String, Error>
+pub fn post_challenge_response<G>(root_certs: &[String], url: &str, data_builder: &G, nonce: &str) -> Result<String, Error>
 where
     G: Fn(&str) -> Result<String, Error>,
 {
-    let (_, _, nonce): (DummyString, String, String) = fetch_obj(url, data_builder, nonce)?;
+    let (_, _, nonce): (DummyString, String, String) = fetch_obj(root_certs, url, data_builder, nonce)?;
     Ok(nonce)
 }
 
 pub fn get_certificate<G>(
+    root_certs: &[String],
     url: &str,
     data_builder: &G,
     nonce: &str,
@@ -224,22 +232,22 @@ pub fn get_certificate<G>(
 where
     G: Fn(&str) -> Result<String, Error>,
 {
-    let (res_body, _, nonce): (DummyString, String, String) = fetch_obj(url, data_builder, nonce)?;
+    let (res_body, _, nonce): (DummyString, String, String) = fetch_obj(root_certs, url, data_builder, nonce)?;
     Ok((res_body.content, nonce))
 }
 
-pub fn get_directory(url: &str) -> Result<Directory, Error> {
+pub fn get_directory(root_certs: &[String], url: &str) -> Result<Directory, Error> {
     let uri = url.parse::<Uri>()?;
-    let mut request = new_request(&uri, Method::GET);
+    let mut request = new_request(root_certs, &uri, Method::GET);
     request.header("Accept", CONTENT_TYPE_JSON);
     let (r, s) = send_request_retry(&request)?;
     check_response(&r, &s)?;
     Directory::from_str(&s)
 }
 
-pub fn get_nonce(url: &str) -> Result<String, Error> {
+pub fn get_nonce(root_certs: &[String], url: &str) -> Result<String, Error> {
     let uri = url.parse::<Uri>()?;
-    let request = new_request(&uri, Method::HEAD);
+    let request = new_request(root_certs, &uri, Method::HEAD);
     let (res, res_body) = send_request_retry(&request)?;
     check_response(&res, &res_body)?;
     nonce_from_response(&res)
diff --git a/acmed/src/main.rs b/acmed/src/main.rs
index 0a86163..e910f40 100644
--- a/acmed/src/main.rs
+++ b/acmed/src/main.rs
@@ -75,6 +75,14 @@ fn main() {
                 .value_name("FILE")
                 .conflicts_with("foregroung"),
         )
+        .arg(
+            Arg::with_name("root-cert")
+            .long("root-cert")
+            .help("Add a root certificate to the trust store")
+            .takes_value(true)
+            .multiple(true)
+            .value_name("FILE")
+        )
         .get_matches();
 
     match acme_common::logs::set_log_system(
@@ -89,13 +97,18 @@ fn main() {
         }
     };
 
+    let root_certs = match matches.values_of("root-cert") {
+        Some(v) => v.collect(),
+        None => vec![],
+    };
+
     init_server(
         matches.is_present("foregroung"),
         matches.value_of("pid-file").unwrap_or(DEFAULT_PID_FILE),
     );
 
     let config_file = matches.value_of("config").unwrap_or(DEFAULT_CONFIG_FILE);
-    let mut srv = match MainEventLoop::new(&config_file) {
+    let mut srv = match MainEventLoop::new(&config_file, &root_certs) {
         Ok(s) => s,
         Err(e) => {
             error!("{}", e);
diff --git a/acmed/src/main_event_loop.rs b/acmed/src/main_event_loop.rs
index 78a3230..d13001a 100644
--- a/acmed/src/main_event_loop.rs
+++ b/acmed/src/main_event_loop.rs
@@ -9,10 +9,11 @@ use std::time::Duration;
 
 pub struct MainEventLoop {
     certs: Vec<Certificate>,
+    root_certs: Vec<String>,
 }
 
 impl MainEventLoop {
-    pub fn new(config_file: &str) -> Result<Self, Error> {
+    pub fn new(config_file: &str, root_certs: &[&str]) -> Result<Self, Error> {
         let cnf = config::from_file(config_file)?;
 
         let mut certs = Vec::new();
@@ -43,7 +44,10 @@ impl MainEventLoop {
             certs.push(cert);
         }
 
-        Ok(MainEventLoop { certs })
+        Ok(MainEventLoop {
+            certs,
+            root_certs: root_certs.iter().map(|v| v.to_string()).collect(),
+        })
     }
 
     pub fn run(&mut self) {
@@ -53,7 +57,7 @@ impl MainEventLoop {
                 match crt.should_renew() {
                     Ok(sr) => {
                         if sr {
-                            let status = match request_certificate(crt) {
+                            let status = match request_certificate(crt, &self.root_certs) {
                                 Ok(_) => "Success.".to_string(),
                                 Err(e) => {
                                     let msg = format!(