diff --git a/acatcher/acatcher.cxx.template b/acatcher/acatcher.cxx.template
index 1ef312f..9b81877 100644
--- a/acatcher/acatcher.cxx.template
+++ b/acatcher/acatcher.cxx.template
@@ -371,7 +371,7 @@ int main(int argc, char *argv[])
 				if ((c >= 'A') && (c <= 'F')) {
 					cur_listener = c + 10 - 'A';
 				}
-				if (old_listener != cur_listener) {
+				if (old_listener != cur_listener && cur_listener <= MAX) {
 					cls();
 					cerr << "Now listening to " << names[cur_listener] << "\r\n";
 				}