diff --git a/BasiliskII/ChangeLog b/BasiliskII/ChangeLog
index b8b605cb..68b4e6b1 100644
--- a/BasiliskII/ChangeLog
+++ b/BasiliskII/ChangeLog
@@ -1,6 +1,8 @@
 V0.9 - <insert date here>
 	- added help for command line arguments, PrefsInit() now removes
 	  all processed options
+	- serial_unix.cpp: input/output_thread_cancel weren't initialized
+	  [Kolja Waschk]
 	- Unix: some performance improvements to VOSF screen update code
 	  [Brian J. Johnson]
 	- Unix: -Ofast option is supplied to MIPSPro compiler [Brian J. Johnson]
diff --git a/BasiliskII/src/Unix/serial_unix.cpp b/BasiliskII/src/Unix/serial_unix.cpp
index 478cf17f..a59f30f8 100644
--- a/BasiliskII/src/Unix/serial_unix.cpp
+++ b/BasiliskII/src/Unix/serial_unix.cpp
@@ -208,6 +208,8 @@ int16 XSERDPort::open(uint16 config)
 	configure(config);
 
 	// Start input/output threads
+	input_thread_cancel = false;
+	output_thread_cancel = false;
 	if (sem_init(&input_signal, 0, 0) < 0)
 		goto open_error;
 	if (sem_init(&output_signal, 0, 0) < 0)