diff --git a/bookwyrm/models/activitypub_mixin.py b/bookwyrm/models/activitypub_mixin.py
index 83ca90b0a..83a7dd998 100644
--- a/bookwyrm/models/activitypub_mixin.py
+++ b/bookwyrm/models/activitypub_mixin.py
@@ -540,10 +540,11 @@ async def sign_and_send(
 
     digest = make_digest(data)
 
+
     headers = {
         "Date": now,
         "Digest": digest,
-        "Signature": make_signature("post", sender, destination, now, digest),
+        "Signature": make_signature("post", sender, destination, now, digest, False),
         "Content-Type": "application/activity+json; charset=utf-8",
         "User-Agent": USER_AGENT,
     }
@@ -554,6 +555,16 @@ async def sign_and_send(
                 logger.exception(
                     "Failed to send broadcast to %s: %s", destination, response.reason
                 )
+                logger.info("Trying again with legacy keyId")
+                # try with incorrect keyId to enable communication with legacy Bookwyrm servers
+                legacy_signature = make_signature("post", sender, destination, now, digest, True)
+                headers["Signature"] = legacy_signature
+                async with session.post(destination, data=data, headers=headers) as response: 
+                    if not response.ok:
+                        logger.exception(
+                        "Failed to send broadcast with legacy keyId to %s: %s", destination, response.reason
+                    )
+                
             return response
     except asyncio.TimeoutError:
         logger.info("Connection timed out for url: %s", destination)
diff --git a/bookwyrm/signatures.py b/bookwyrm/signatures.py
index 3dfde4cb1..2a1f2e72a 100644
--- a/bookwyrm/signatures.py
+++ b/bookwyrm/signatures.py
@@ -22,7 +22,7 @@ def create_key_pair():
     return private_key, public_key
 
 
-def make_signature(method, sender, destination, date, digest=None):
+def make_signature(method, sender, destination, date, digest=None, use_legacy_key=False):
     """uses a private key to sign an outgoing message"""
     inbox_parts = urlparse(destination)
     signature_headers = [
@@ -38,8 +38,10 @@ def make_signature(method, sender, destination, date, digest=None):
     message_to_sign = "\n".join(signature_headers)
     signer = pkcs1_15.new(RSA.import_key(sender.key_pair.private_key))
     signed_message = signer.sign(SHA256.new(message_to_sign.encode("utf8")))
+    # For legacy reasons we need to use an incorrect keyId for older Bookwyrm versions
+    key_id = f"{sender.remote_id}#main-key" if use_legacy_key else f"{sender.remote_id}/#main-key"
     signature = {
-        "keyId": f"{sender.remote_id}/#main-key",
+        "keyId": key_id,
         "algorithm": "rsa-sha256",
         "headers": headers,
         "signature": b64encode(signed_message).decode("utf8"),
diff --git a/bookwyrm/views/inbox.py b/bookwyrm/views/inbox.py
index da32ebdb0..9eef6792f 100644
--- a/bookwyrm/views/inbox.py
+++ b/bookwyrm/views/inbox.py
@@ -137,7 +137,8 @@ def has_valid_signature(request, activity):
             return False
 
         if signature.key_id != remote_user.key_pair.remote_id:
-            raise ValueError("Wrong actor created signature.")
+            if signature.key_id != f"{remote_user.remote_id}#main-key": # legacy Bookwyrm
+                raise ValueError("Wrong actor created signature.")
 
         try:
             signature.verify(remote_user.key_pair.public_key, request)