diff --git a/modules/paxmon/src/rt_updates.cc b/modules/paxmon/src/rt_updates.cc
index 52ee30726..5f2371709 100644
--- a/modules/paxmon/src/rt_updates.cc
+++ b/modules/paxmon/src/rt_updates.cc
@@ -42,13 +42,15 @@ void check_broken_interchanges(
     auto const to = ice->to(uv);
     auto const ic = static_cast<int>(to->current_time()) -
                     static_cast<int>(from->current_time());
-    auto const early_departure = static_cast<int>(to->schedule_time()) -
-                                 static_cast<int>(to->current_time());
+    auto const early_departure = to->current_time() < to->schedule_time()
+                                     ? static_cast<int>(to->schedule_time()) -
+                                           static_cast<int>(to->current_time())
+                                     : 0;
     if (ice->is_canceled(uv) ||
         (from->station_ != 0 && to->station_ != 0 &&
          ic < ice->transfer_time()) ||
         (from->station_ == 0 &&
-         early_departure <= uv.early_departure_tolerance_)) {
+         early_departure > uv.early_departure_tolerance_)) {
       if (ice->broken_) {
         continue;
       }