diff --git a/lib/utils/interrupt_char.c b/lib/utils/interrupt_char.c
index fca0f95b5..43d45e5ae 100644
--- a/lib/utils/interrupt_char.c
+++ b/lib/utils/interrupt_char.c
@@ -29,7 +29,7 @@
 
 #if MICROPY_KBD_EXCEPTION
 
-int mp_interrupt_char;
+int mp_interrupt_char = -1;
 
 void mp_hal_set_interrupt_char(int c) {
     if (c != -1) {