diff --git a/artiq/devices/core_dds.py b/artiq/devices/core_dds.py
index 27a7fd5cf..cb95ad910 100644
--- a/artiq/devices/core_dds.py
+++ b/artiq/devices/core_dds.py
@@ -11,8 +11,8 @@ class DDS:
 
 		self._previous_frequency = 0*MHz
 
-	kernel_attr_ro = {"reg_channel", "rtio_channel", "latency", "phase_mode"}
-	kernel_attr = {"_previous_frequency"}
+	kernel_attr_ro = "reg_channel rtio_channel latency phase_mode"
+	kernel_attr = "_previous_frequency"
 
 	@kernel
 	def pulse(self, frequency, duration):
diff --git a/artiq/language/experiment.py b/artiq/language/experiment.py
index 9e0333019..5b7f0395a 100644
--- a/artiq/language/experiment.py
+++ b/artiq/language/experiment.py
@@ -5,9 +5,7 @@ class Experiment:
 	parameters = ""
 
 	def __init__(self, *args, **kwargs):
-		channels = self.channels.split()
-		parameters = self.parameters.split()
-		argnames = channels + parameters
+		argnames = self.channels.split() + self.parameters.split()
 		undef_args = list(argnames)
 
 		if len(argnames) < len(args):
@@ -23,7 +21,7 @@ class Experiment:
 			raise TypeError("__init__() missing {} argument(s): ".format(len(undef_args),
 				", ".join(["'"+s+"'" for s in undef_args])))
 
-		self.kernel_attr_ro = set(parameters)
+		self.kernel_attr_ro = self.parameters
 
 def kernel(arg):
 	if isinstance(arg, str):