diff --git a/artiq/compiler/ir_values.py b/artiq/compiler/ir_values.py
index cdb331c21..ad6c0d1bb 100644
--- a/artiq/compiler/ir_values.py
+++ b/artiq/compiler/ir_values.py
@@ -115,6 +115,12 @@ class VBool(VInt):
 	def create_constant(self, b):
 		VInt.create_constant(self, int(b))
 
+	def o_bool(self, builder):
+		if builder is None:
+			return VBool()
+		else:
+			return self
+
 # Operators
 
 def _make_unary_operator(op_name):