diff --git a/src/allmydata/grid_manager.py b/src/allmydata/grid_manager.py
index 4c16b572a..fde88824e 100644
--- a/src/allmydata/grid_manager.py
+++ b/src/allmydata/grid_manager.py
@@ -346,7 +346,7 @@ def validate_grid_manager_certificate(gm_key, alleged_cert):
     return cert
 
 
-def create_grid_manager_verifier(keys, certs, now_fn=None, bad_cert=None):
+def create_grid_manager_verifier(keys, certs, public_key, now_fn=None, bad_cert=None):
     """
     Creates a predicate for confirming some Grid Manager-issued
     certificates against Grid Manager keys. A predicate is used
@@ -358,6 +358,9 @@ def create_grid_manager_verifier(keys, certs, now_fn=None, bad_cert=None):
     :param list certs: 1 or more Grid Manager certificates each of
         which is a `dict` containing 'signature' and 'certificate' keys.
 
+    :param str public_key: the identifier of the server we expect
+        certificates for.
+
     :param callable now_fn: a callable which returns the current UTC
         timestamp (or datetime.utcnow if None).
 
@@ -416,10 +419,11 @@ def create_grid_manager_verifier(keys, certs, now_fn=None, bad_cert=None):
         # if *any* certificate is still valid then we consider the server valid
         for cert in valid_certs:
             expires = datetime.utcfromtimestamp(cert['expires'])
-            # cert_pubkey = keyutil.parse_pubkey(cert['public_key'].encode('ascii'))
-            if expires > now:
-                # not-expired
-                return True
+            cert_pubkey = ed25519.verifying_key_from_string(cert['public_key'].encode('ascii'))
+            if cert['public_key'] == public_key:
+                if expires > now:
+                    # not-expired
+                    return True
         return False
 
     return validate
diff --git a/src/allmydata/storage_client.py b/src/allmydata/storage_client.py
index aa8431e05..293683f66 100644
--- a/src/allmydata/storage_client.py
+++ b/src/allmydata/storage_client.py
@@ -285,6 +285,7 @@ class StorageFarmBroker(service.MultiService):
         gm_verifier = create_grid_manager_verifier(
             self.storage_client_config.grid_manager_keys,
             server["ann"].get("grid-manager-certificates", []),
+            "pub-{}".format(server_id),  # server_id is v0-<key> not pub-v0-key .. for reasons?
         )
 
         s = NativeStorageServer(
diff --git a/src/allmydata/test/test_grid_manager.py b/src/allmydata/test/test_grid_manager.py
index bcea741d7..5323a6548 100644
--- a/src/allmydata/test/test_grid_manager.py
+++ b/src/allmydata/test/test_grid_manager.py
@@ -287,6 +287,7 @@ class GridManagerVerifier(SyncTestCase):
         verify = create_grid_manager_verifier(
             [self.gm._public_key],
             [cert0],
+            ed25519.string_from_verifying_key(pub0),
         )
 
         self.assertTrue(verify())