diff --git a/lib/charms/observability_libs/v0/cert_handler.py b/lib/charms/observability_libs/v0/cert_handler.py
index 07d9063..9dcfc8f 100644
--- a/lib/charms/observability_libs/v0/cert_handler.py
+++ b/lib/charms/observability_libs/v0/cert_handler.py
@@ -67,7 +67,7 @@
 
 LIBID = "b5cd5cd580f3428fa5f59a8876dcbe6a"
 LIBAPI = 0
-LIBPATCH = 10
+LIBPATCH = 11
 
 
 def is_ip_address(value: str) -> bool:
@@ -378,7 +378,15 @@ def _server_cert(self, value: str):
     def _chain(self) -> str:
         if self._peer_relation:
             if chain := self._peer_relation.data[self.charm.unit].get("chain", ""):
-                return json.loads(cast(str, chain))
+                chain = json.loads(chain)
+
+                # In a previous version of this lib, chain used to be a list.
+                # Convert the List[str] to str, per
+                # https://github.com/canonical/tls-certificates-interface/pull/141
+                if isinstance(chain, list):
+                    chain = "\n\n".join(reversed(chain))
+
+                return cast(str, chain)
         return ""
 
     @_chain.setter
diff --git a/lib/charms/observability_libs/v1/cert_handler.py b/lib/charms/observability_libs/v1/cert_handler.py
index 4c43fe4..1375550 100644
--- a/lib/charms/observability_libs/v1/cert_handler.py
+++ b/lib/charms/observability_libs/v1/cert_handler.py
@@ -32,18 +32,17 @@
 Since this library uses [Juju Secrets](https://juju.is/docs/juju/secret) it requires Juju >= 3.0.3.
 """
 import ipaddress
-import json
 import socket
 from itertools import filterfalse
 from typing import List, Optional, Union
 
 try:
-    from charms.tls_certificates_interface.v2.tls_certificates import (  # type: ignore
+    from charms.tls_certificates_interface.v3.tls_certificates import (  # type: ignore
         AllCertificatesInvalidatedEvent,
         CertificateAvailableEvent,
         CertificateExpiringEvent,
         CertificateInvalidatedEvent,
-        TLSCertificatesRequiresV2,
+        TLSCertificatesRequiresV3,
         generate_csr,
         generate_private_key,
     )
@@ -66,7 +65,7 @@
 
 LIBID = "b5cd5cd580f3428fa5f59a8876dcbe6a"
 LIBAPI = 1
-LIBPATCH = 3
+LIBPATCH = 4
 
 
 def is_ip_address(value: str) -> bool:
@@ -128,7 +127,7 @@ def __init__(
         self.sans_dns = list(filterfalse(is_ip_address, sans))
 
         self.certificates_relation_name = certificates_relation_name
-        self.certificates = TLSCertificatesRequiresV2(self.charm, self.certificates_relation_name)
+        self.certificates = TLSCertificatesRequiresV3(self.charm, self.certificates_relation_name)
 
         self.framework.observe(
             self.charm.on.config_changed,
@@ -278,7 +277,7 @@ def _on_certificate_available(self, event: CertificateAvailableEvent) -> None:
             content = {
                 "ca-cert": event.ca,
                 "server-cert": event.certificate,
-                "chain": json.dumps(event.chain),
+                "chain": event.chain_as_pem(),
                 "csr": event_csr,
             }
             try:
diff --git a/tests/integration/conftest.py b/tests/integration/conftest.py
index 8426fb5..ad5470d 100644
--- a/tests/integration/conftest.py
+++ b/tests/integration/conftest.py
@@ -79,7 +79,7 @@ async def tester_charm(ops_test: OpsTest) -> Path:
     fetch_tls_cmd = [
         "charmcraft",
         "fetch-lib",
-        "charms.tls_certificates_interface.v2.tls_certificates",
+        "charms.tls_certificates_interface.v3.tls_certificates",
     ]
     await ops_test.run(*fetch_tls_cmd)
     shutil.move("lib/charms/tls_certificates_interface", f"{TESTINGCHARM_PATH}/lib/charms/")