diff --git a/artiq/management/pc_rpc.py b/artiq/management/pc_rpc.py
index 92e31ef2a..dcb4ccdc7 100644
--- a/artiq/management/pc_rpc.py
+++ b/artiq/management/pc_rpc.py
@@ -1,8 +1,9 @@
 import socket
-import json
 import asyncio
 import traceback
 
+from artiq.management import pyon
+
 
 class RemoteError(Exception):
     pass
@@ -17,7 +18,7 @@ class Client:
 
     def do_rpc(self, name, args, kwargs):
         obj = {"action": "call", "name": name, "args": args, "kwargs": kwargs}
-        line = json.dumps(obj) + "\n"
+        line = pyon.encode(obj) + "\n"
         self.socket.sendall(line.encode())
 
         buf = self.socket.recv(4096).decode()
@@ -26,7 +27,7 @@ class Client:
             if not more:
                 break
             buf += more.decode()
-        obj = json.loads(buf)
+        obj = pyon.decode(buf)
         if obj["result"] == "ok":
             return obj["ret"]
         elif obj["result"] == "error":
@@ -73,7 +74,7 @@ class Server:
                 line = yield from reader.readline()
                 if not line:
                     break
-                obj = json.loads(line.decode())
+                obj = pyon.decode(line.decode())
                 action = obj["action"]
                 if action == "call":
                     method = getattr(self.target, obj["name"])
diff --git a/artiq/management/pyon.py b/artiq/management/pyon.py
new file mode 100644
index 000000000..3465ae0e2
--- /dev/null
+++ b/artiq/management/pyon.py
@@ -0,0 +1,73 @@
+import base64
+
+import numpy
+
+
+def _encode_none(x):
+    return "None"
+
+
+def _encode_number(x):
+    return str(x)
+
+
+def _encode_str(x):
+    return repr(x)
+
+
+def _encode_tuple(x):
+    if len(x) == 1:
+        return "(" + encode(x[0]) + ", )"
+    else:
+        r = "("
+        r += ", ".join([encode(item) for item in x])
+        r += ")"
+        return r
+
+
+def _encode_list(x):
+    r = "["
+    r += ", ".join([encode(item) for item in x])
+    r += "]"
+    return r
+
+
+def _encode_dict(x):
+    r = "{"
+    r += ", ".join([encode(k) + ": " + encode(v) for k, v in x.items()])
+    r += "}"
+    return r
+
+
+def _encode_nparray(x):
+    r = "nparray("
+    r += encode(x.shape) + ", "
+    r += encode(str(x.dtype)) + ", "
+    r += encode(base64.b64encode(x).decode())
+    r += ")"
+    return r
+
+
+_encode_map = {
+    type(None): _encode_none,
+    int: _encode_number,
+    float: _encode_number,
+    str: _encode_str,
+    tuple: _encode_tuple,
+    list: _encode_list,
+    dict: _encode_dict,
+    numpy.ndarray: _encode_nparray
+}
+
+
+def encode(x):
+    return _encode_map[type(x)](x)
+
+
+def _nparray(shape, dtype, data):
+    a = numpy.frombuffer(base64.b64decode(data), dtype=dtype)
+    return a.reshape(shape)
+
+
+def decode(s):
+    return eval(s, {"__builtins__": None, "nparray": _nparray}, {})