diff --git a/Components/68901/MFP68901.cpp b/Components/68901/MFP68901.cpp
index 6c9f211e8..3d41cb7e9 100644
--- a/Components/68901/MFP68901.cpp
+++ b/Components/68901/MFP68901.cpp
@@ -321,7 +321,11 @@ bool MFP68901::get_interrupt_line() {
 	return interrupt_line_;
 }
 
-uint8_t MFP68901::acknowledge_interrupt() {
+int MFP68901::acknowledge_interrupt() {
+	if(!(interrupt_pending_ & interrupt_mask_)) {
+		return NoAcknowledgement;
+	}
+
 	const int selected = fls(interrupt_pending_ & interrupt_mask_) - 1;
 	const int mask = 1 << selected;
 
diff --git a/Components/68901/MFP68901.hpp b/Components/68901/MFP68901.hpp
index a9d4325ff..f1a930820 100644
--- a/Components/68901/MFP68901.hpp
+++ b/Components/68901/MFP68901.hpp
@@ -36,7 +36,9 @@ class MFP68901: public ClockingHint::Source {
 		uint8_t get_port_output();
 
 		bool get_interrupt_line();
-		uint8_t acknowledge_interrupt();
+
+		const int NoAcknowledgement = 0x100;
+		int acknowledge_interrupt();
 
 		struct InterruptDelegate {
 			virtual void mfp68901_did_change_interrupt_status(MFP68901 *) = 0;