diff --git a/docs/production/index.rst b/docs/production/index.rst
index b91ed6bd..67e97dae 100644
--- a/docs/production/index.rst
+++ b/docs/production/index.rst
@@ -451,3 +451,53 @@ LetsEncrypt flow to function. However, Lemur will attempt to automatically deter
 possible. To enable this functionality, periodically (or through Cron/Celery) run `lemur dns_providers get_all_zones`.
 This command will traverse all DNS providers, determine which zones they control, and upload this list of zones to
 Lemur's database (in the dns_providers table). Alternatively, you can manually input this data.
+
+
+LetsEncrypt: pinning to cross-signed ICA
+----------------------------------------
+
+Let's Encrypt has been using a `cross-signed <https://letsencrypt.org/certificates/>`_ intermediate CA by DST Root CA X3,
+which is included in many older devices' TrustStore.
+
+
+Let's Encrypt is `transitioning <https://letsencrypt.org/2019/04/15/transitioning-to-isrg-root.html>`_ to use
+the intermediate CA issued by their own root (ISRG X1) starting from September 29th 2020.
+This is in preparation of concluding the initial bootstrapping of their CA, by having it cross-signed by an older CA.
+
+
+Lemur can temporarily pin to the cross-signed intermediate CA (same public/private key pair as the ICA signed by ISRG X1).
+This will prolong support for incompatible devices.
+
+The following must be added to the config file to activate the pinning (the pinning will be removed by September 2021)::
+
+    # remove or update after Mar 17 16:40:46 2021 GMT
+    IDENTRUST_CROSS_SIGNED_LE_ICA_EXPIRATION_DATE = "17/03/21"
+    IDENTRUST_CROSS_SIGNED_LE_ICA = """
+    -----BEGIN CERTIFICATE-----
+    MIIEkjCCA3qgAwIBAgIQCgFBQgAAAVOFc2oLheynCDANBgkqhkiG9w0BAQsFADA/
+    MSQwIgYDVQQKExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMT
+    DkRTVCBSb290IENBIFgzMB4XDTE2MDMxNzE2NDA0NloXDTIxMDMxNzE2NDA0Nlow
+    SjELMAkGA1UEBhMCVVMxFjAUBgNVBAoTDUxldCdzIEVuY3J5cHQxIzAhBgNVBAMT
+    GkxldCdzIEVuY3J5cHQgQXV0aG9yaXR5IFgzMIIBIjANBgkqhkiG9w0BAQEFAAOC
+    AQ8AMIIBCgKCAQEAnNMM8FrlLke3cl03g7NoYzDq1zUmGSXhvb418XCSL7e4S0EF
+    q6meNQhY7LEqxGiHC6PjdeTm86dicbp5gWAf15Gan/PQeGdxyGkOlZHP/uaZ6WA8
+    SMx+yk13EiSdRxta67nsHjcAHJyse6cF6s5K671B5TaYucv9bTyWaN8jKkKQDIZ0
+    Z8h/pZq4UmEUEz9l6YKHy9v6Dlb2honzhT+Xhq+w3Brvaw2VFn3EK6BlspkENnWA
+    a6xK8xuQSXgvopZPKiAlKQTGdMDQMc2PMTiVFrqoM7hD8bEfwzB/onkxEz0tNvjj
+    /PIzark5McWvxI0NHWQWM6r6hCm21AvA2H3DkwIDAQABo4IBfTCCAXkwEgYDVR0T
+    AQH/BAgwBgEB/wIBADAOBgNVHQ8BAf8EBAMCAYYwfwYIKwYBBQUHAQEEczBxMDIG
+    CCsGAQUFBzABhiZodHRwOi8vaXNyZy50cnVzdGlkLm9jc3AuaWRlbnRydXN0LmNv
+    bTA7BggrBgEFBQcwAoYvaHR0cDovL2FwcHMuaWRlbnRydXN0LmNvbS9yb290cy9k
+    c3Ryb290Y2F4My5wN2MwHwYDVR0jBBgwFoAUxKexpHsscfrb4UuQdf/EFWCFiRAw
+    VAYDVR0gBE0wSzAIBgZngQwBAgEwPwYLKwYBBAGC3xMBAQEwMDAuBggrBgEFBQcC
+    ARYiaHR0cDovL2Nwcy5yb290LXgxLmxldHNlbmNyeXB0Lm9yZzA8BgNVHR8ENTAz
+    MDGgL6AthitodHRwOi8vY3JsLmlkZW50cnVzdC5jb20vRFNUUk9PVENBWDNDUkwu
+    Y3JsMB0GA1UdDgQWBBSoSmpjBH3duubRObemRWXv86jsoTANBgkqhkiG9w0BAQsF
+    AAOCAQEA3TPXEfNjWDjdGBX7CVW+dla5cEilaUcne8IkCJLxWh9KEik3JHRRHGJo
+    uM2VcGfl96S8TihRzZvoroed6ti6WqEBmtzw3Wodatg+VyOeph4EYpr/1wXKtx8/
+    wApIvJSwtmVi4MFU5aMqrSDE6ea73Mj2tcMyo5jMd6jmeWUHK8so/joWUoHOUgwu
+    X4Po1QYz+3dszkDqMp4fklxBwXRsW10KXzPMTZ+sOPAveyxindmjkW8lGy+QsRlG
+    PfZ+G6Z6h7mjem0Y+iWlkYcV4PIWL1iwBi8saCbGS5jN2p8M+X+Q7UNKEkROb3N6
+    KOqkqm57TH2H3eDJAkSnh6/DNFu0Qg==
+    -----END CERTIFICATE-----
+    """
diff --git a/lemur/plugins/lemur_acme/plugin.py b/lemur/plugins/lemur_acme/plugin.py
index 3fc1df61..16d61a0f 100644
--- a/lemur/plugins/lemur_acme/plugin.py
+++ b/lemur/plugins/lemur_acme/plugin.py
@@ -205,9 +205,15 @@ class AcmeHandler(object):
                 OpenSSL.crypto.FILETYPE_PEM, orderr.fullchain_pem
             ),
         ).decode()
-        pem_certificate_chain = orderr.fullchain_pem[
-            len(pem_certificate) :  # noqa
-        ].lstrip()
+
+        if current_app.config.get("IDENTRUST_CROSS_SIGNED_LE_ICA", False) \
+                and datetime.datetime.now() < datetime.datetime.strptime(
+                    current_app.config.get("IDENTRUST_CROSS_SIGNED_LE_ICA_EXPIRATION_DATE", "17/03/21"), '%d/%m/%y'):
+            pem_certificate_chain = current_app.config.get("IDENTRUST_CROSS_SIGNED_LE_ICA")
+        else:
+            pem_certificate_chain = orderr.fullchain_pem[
+                len(pem_certificate) :  # noqa
+            ].lstrip()
 
         current_app.logger.debug(
             "{0} {1}".format(type(pem_certificate), type(pem_certificate_chain))
diff --git a/lemur/plugins/lemur_acme/tests/test_acme.py b/lemur/plugins/lemur_acme/tests/test_acme.py
index 94949a74..8320a2de 100644
--- a/lemur/plugins/lemur_acme/tests/test_acme.py
+++ b/lemur/plugins/lemur_acme/tests/test_acme.py
@@ -156,6 +156,7 @@ class TestAcme(unittest.TestCase):
         mock_acme.fetch_chain = Mock(return_value="mock_chain")
         mock_crypto.dump_certificate = Mock(return_value=b"chain")
         mock_order = Mock()
+        mock_current_app.config = {}
         self.acme.request_certificate(mock_acme, [], mock_order)
 
     def test_setup_acme_client_fail(self):