diff --git a/converter/ibmpc_usb/config.h b/converter/ibmpc_usb/config.h
index fc545f69..0198f5e1 100644
--- a/converter/ibmpc_usb/config.h
+++ b/converter/ibmpc_usb/config.h
@@ -75,7 +75,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
               (0<<ISC10));      \
 } while (0)
 
+/* NOTE: clear flag and enabling to ditch unwanted interrupt */
 #define IBMPC_INT_ON()  do {    \
+    EIFR  |= (1<<INTF1);        \
     EIMSK |= (1<<INT1);         \
 } while (0)