diff --git a/modules/fediverse/ap_security.py b/modules/fediverse/ap_security.py
index f7d17a2e..a466aaa5 100644
--- a/modules/fediverse/ap_security.py
+++ b/modules/fediverse/ap_security.py
@@ -1,9 +1,14 @@
 import base64, typing
 
 try:
+    from cryptography import x509
     from cryptography.hazmat.primitives import hashes, serialization
     from cryptography.hazmat.primitives.asymmetric import padding, rsa
     from cryptography.hazmat.backends import default_backend
+
+    from cryptography.hazmat.primitives.serialization import Encoding
+    from cryptography.hazmat.primitives.serialization import PublicFormat
+
     has_crypto = True
 except ModuleNotFoundError:
     has_crypto = False
@@ -21,6 +26,13 @@ class PrivateKey(object):
         self.key = _private_key(filename)
         self.id = id
 
+def public_key(key_filename: str) -> str:
+    with open(key_filename, "rb") as key_file:
+        cert = x509.load_pem_x509_certificate(key_file.read(),
+            default_backend())
+    return cert.public_key().public_bytes(
+        Encoding.PEM, PublicFormat.SubjectPublicKeyInfo).decode("ascii")
+
 def signature(key: PrivateKey, headers: typing.List[typing.Tuple[str, str]]
         ) -> str:
     sign_header_keys = " ".join(h[0].lower() for h in headers)
diff --git a/modules/fediverse/ap_server.py b/modules/fediverse/ap_server.py
index 89b884a4..d4ae9044 100644
--- a/modules/fediverse/ap_server.py
+++ b/modules/fediverse/ap_server.py
@@ -138,8 +138,7 @@ class Server(object):
             outbox = self._ap_outbox_url(event["url_for"])
 
             cert_filename = self.bot.config["tls-certificate"]
-            with open(cert_filename) as cert_file:
-                cert = cert_file.read()
+            pubkey = ap_security.public_key(cert_filename)
 
             event["response"].content_type = ap_utils.LD_TYPE
             event["response"].write_json({
@@ -153,7 +152,7 @@ class Server(object):
                 "publicKey": {
                     "id": "%s#key" % self_id,
                     "owner": self_id,
-                    "publicKeyPem": cert
+                    "publicKeyPem": pubkey
                 }
             })
         else: