diff --git a/artiq/coredevice/comm_generic.py b/artiq/coredevice/comm_generic.py
index 637f94d32..8d8dccf87 100644
--- a/artiq/coredevice/comm_generic.py
+++ b/artiq/coredevice/comm_generic.py
@@ -512,7 +512,7 @@ class CommGeneric:
             assert exception.id != 0
             python_exn_type = object_map.retrieve(exception.id)
 
-        python_exn = python_exn_type(message)
+        python_exn = python_exn_type(message.format(*params))
         python_exn.artiq_exception = exception
         raise python_exn