diff --git a/artiq/coredevice/comm_kernel.py b/artiq/coredevice/comm_kernel.py
index 77f1ed74d..670d2cc41 100644
--- a/artiq/coredevice/comm_kernel.py
+++ b/artiq/coredevice/comm_kernel.py
@@ -658,10 +658,10 @@ class CommKernel:
         return_tags = self._read_bytes()
 
         if service_id == 0:
-            def service(header, *values):
+            def service(*values):
                 counter = 0
-                for obj in json.loads(header):
-                    old_val = embedding_map.globals_map[obj["id"]]
+                for obj in embedding_map.attributes_writeback:
+                    old_val = obj["obj"]
                     if "fields" in obj:
                         for name in obj["fields"]:
                             setattr(old_val, name, values[counter])
diff --git a/artiq/language/embedding_map.py b/artiq/language/embedding_map.py
index 64a041a6f..466426121 100644
--- a/artiq/language/embedding_map.py
+++ b/artiq/language/embedding_map.py
@@ -9,7 +9,7 @@ class EmbeddingMap:
         self.string_map = {}
         self.string_reverse_map = {}
         self.function_map = {}
-        self.globals_map = {}
+        self.attributes_writeback = []
 
         # preallocate exception names
         # must be kept in sync with EXCEPTION_ID_LOOKUP in artiq/firmware/ksupport/eh_artiq.rs,