diff --git a/Components/6850/6850.cpp b/Components/6850/6850.cpp
index 80a0afdcf..35c01a85b 100644
--- a/Components/6850/6850.cpp
+++ b/Components/6850/6850.cpp
@@ -89,6 +89,7 @@ void ACIA::write(int address, uint8_t value) {
 					transmit.write(false);
 				break;
 			}
+			receive.set_read_delegate(this, Storage::Time(divider_ * 2, receive_clock_rate_.as_int()));
 			receive_interrupt_enabled_ = value & 0x80;
 		}
 	}
@@ -174,3 +175,8 @@ ClockingHint::Preference ACIA::preferred_clocking() {
 bool ACIA::get_interrupt_line() const {
 	return interrupt_request_;
 }
+
+bool ACIA::serial_line_did_produce_bit(Serial::Line *line, int bit) {
+	// TODO: how does this affect signalling?
+	return false;
+}
diff --git a/Components/6850/6850.hpp b/Components/6850/6850.hpp
index e901814c4..4509cfe5e 100644
--- a/Components/6850/6850.hpp
+++ b/Components/6850/6850.hpp
@@ -17,7 +17,7 @@
 namespace Motorola {
 namespace ACIA {
 
-class ACIA: public ClockingHint::Source {
+class ACIA: public ClockingHint::Source, private Serial::Line::ReadDelegate {
 	public:
 		static constexpr const HalfCycles SameAsTransmit = HalfCycles(0);
 
@@ -85,6 +85,8 @@ class ACIA: public ClockingHint::Source {
 
 		HalfCycles transmit_clock_rate_;
 		HalfCycles receive_clock_rate_;
+
+		bool serial_line_did_produce_bit(Serial::Line *line, int bit) final;
 };
 
 }
diff --git a/Components/SerialPort/SerialPort.cpp b/Components/SerialPort/SerialPort.cpp
index 7ecdde52c..2131e6bf1 100644
--- a/Components/SerialPort/SerialPort.cpp
+++ b/Components/SerialPort/SerialPort.cpp
@@ -103,6 +103,7 @@ bool Line::read() {
 void Line::set_read_delegate(ReadDelegate *delegate, Storage::Time bit_length) {
 	read_delegate_ = delegate;
 	read_delegate_bit_length_ = bit_length;
+	read_delegate_bit_length_.simplify();
 	write_cycles_since_delegate_call_ = 0;
 }