diff --git a/artiq/gateware/targets/kasli.py b/artiq/gateware/targets/kasli.py
index 77c1460e1..e45c57ff1 100755
--- a/artiq/gateware/targets/kasli.py
+++ b/artiq/gateware/targets/kasli.py
@@ -240,7 +240,7 @@ class Opticlock(_StandaloneBase):
         _StandaloneBase.__init__(self, **kwargs)
 
         self.config["SI5324_AS_SYNTHESIZER"] = None
-        self.config["SI5324_EXT_REF"] = None
+        # self.config["SI5324_EXT_REF"] = None
         self.config["RTIO_FREQUENCY"] = "125.0"
 
         platform = self.platform