diff --git a/src/main.c b/src/main.c
index 8441a67..0466757 100644
--- a/src/main.c
+++ b/src/main.c
@@ -147,11 +147,17 @@ int main(int argc, char **argv)
             rtty.devid = optarg;
             break;
         case 'i':
-            rtty.heartbeat = atof(optarg);
+            rtty.heartbeat = atoi(optarg);
+
             if (rtty.heartbeat < 5) {
-                rtty.heartbeat = 5.0;
+                rtty.heartbeat = 5;
                 log_warn("Heartbeat interval too short, set to 5s\n");
             }
+
+            if (rtty.heartbeat > 255) {
+                rtty.heartbeat = 255;
+                log_warn("Heartbeat interval too long, set to 255s\n");
+            }
             break;
         case 'h':
             rtty.host = optarg;
diff --git a/src/rtty.h b/src/rtty.h
index 9951eb2..1e28844 100644
--- a/src/rtty.h
+++ b/src/rtty.h
@@ -95,7 +95,7 @@ struct rtty {
     struct ev_io ior;
     struct ev_timer tmr;
     struct ev_loop *loop;
-    ev_tstamp heartbeat;
+    int heartbeat;
     bool wait_heartbeat;
     bool registered;
     bool reconnect;