diff --git a/include/navparser.hpp b/include/navparser.hpp
index d56045c2..8b96ab2a 100644
--- a/include/navparser.hpp
+++ b/include/navparser.hpp
@@ -38,8 +38,12 @@ class inactivityTracker
 
     bool vischeckConnection(std::pair<int, int> &connection)
     {
-        Vector begin = areas.at(FindInVector(connection.first)).m_center;
-        Vector end   = areas.at(FindInVector(connection.second)).m_center;
+        int id0 = FindInVector(connection.first);
+        int id1 = FindInVector(connection.second);
+        if (id0 == -1 || id1 == -1)
+            return false;
+        Vector begin = areas.at(id0).m_center;
+        Vector end   = areas.at(id1).m_center;
         begin.z += 72;
         end.z += 72;
         bool result = IsVectorVisible(begin, end, false);
diff --git a/src/navparser.cpp b/src/navparser.cpp
index f9739f5f..ea4ec0e5 100644
--- a/src/navparser.cpp
+++ b/src/navparser.cpp
@@ -24,6 +24,7 @@ size_t FindInVector(size_t id)
         if (areas.at(i).m_id == id)
             return i;
     }
+    return -1;
 }
 
 void Init()