diff --git a/libagent/gpg/agent.py b/libagent/gpg/agent.py
index e60b3e9..92bb2d7 100644
--- a/libagent/gpg/agent.py
+++ b/libagent/gpg/agent.py
@@ -124,7 +124,7 @@ class Handler(object):
             raise AgentError(b'ERR 100696144 No such device <SCD>')
         keyring.sendline(conn, b'D ' + reply)
 
-    @util.memoize
+    @util.memoize_method  # global cache for key grips
     def get_identity(self, keygrip):
         """
         Returns device.interface.Identity that matches specified keygrip.
@@ -171,7 +171,6 @@ class Handler(object):
         ec_point = self.client.ecdh(identity=identity, pubkey=remote_pubkey)
         keyring.sendline(conn, b'D ' + _serialize_point(ec_point))
 
-    @util.memoize
     def have_key(self, *keygrips):
         """Check if any keygrip corresponds to a TREZOR-based key."""
         for keygrip in keygrips:
diff --git a/libagent/util.py b/libagent/util.py
index 623ddda..c98891f 100644
--- a/libagent/util.py
+++ b/libagent/util.py
@@ -215,6 +215,24 @@ def memoize(func):
     return wrapper
 
 
+def memoize_method(method):
+    """Simple caching decorator."""
+    cache = {}
+
+    @functools.wraps(method)
+    def wrapper(self, *args, **kwargs):
+        """Caching wrapper."""
+        key = (args, tuple(sorted(kwargs.items())))
+        if key in cache:
+            return cache[key]
+        else:
+            result = method(self, *args, **kwargs)
+            cache[key] = result
+            return result
+
+    return wrapper
+
+
 @memoize
 def which(cmd):
     """Return full path to specified command, or raise OSError if missing."""