diff --git a/artiq/coredevice/core.py b/artiq/coredevice/core.py
index 2afc898ad..9addf1b3c 100644
--- a/artiq/coredevice/core.py
+++ b/artiq/coredevice/core.py
@@ -2,6 +2,7 @@ import os
 
 from artiq.language.core import *
 from artiq.language.db import *
+from artiq.language.units import ns
 
 from artiq.transforms.inline import inline
 from artiq.transforms.lower_units import lower_units
@@ -47,7 +48,7 @@ def _no_debug_unparse(label, node):
 class Core(AutoDB):
     class DBKeys:
         comm = Device()
-        ref_period = Argument()
+        ref_period = Argument(8*ns)
         external_clock = Argument(False)
 
     def build(self):
diff --git a/benchmarks/ddb.pyon b/benchmarks/ddb.pyon
index 6217b00c7..3842a5e18 100644
--- a/benchmarks/ddb.pyon
+++ b/benchmarks/ddb.pyon
@@ -9,7 +9,7 @@
         "type": "local",
         "module": "artiq.coredevice.core",
         "class": "Core",
-        "arguments": {"ref_period": Quantity(Fraction(8, 1000000000), "s")}
+        "arguments": {}
     },
 
     "pmt0": {
diff --git a/examples/master/ddb.pyon b/examples/master/ddb.pyon
index a5855969e..b602d367a 100644
--- a/examples/master/ddb.pyon
+++ b/examples/master/ddb.pyon
@@ -9,7 +9,7 @@
         "type": "local",
         "module": "artiq.coredevice.core",
         "class": "Core",
-        "arguments": {"ref_period": Quantity(Fraction(8, 1000000000), "s")}
+        "arguments": {}
     },
 
     "pmt0": {