diff --git a/messaging/__init__.py b/messaging/__init__.py
index cc138a03d..a2695bda2 100644
--- a/messaging/__init__.py
+++ b/messaging/__init__.py
@@ -168,9 +168,8 @@ def __init__(self, services: List[str], poll: Optional[str] = None,
     self.ignore_average_freq = [] if ignore_avg_freq is None else ignore_avg_freq
     self.ignore_alive = [] if ignore_alive is None else ignore_alive
     self.ignore_valid = [] if ignore_valid is None else ignore_valid
-    if bool(int(os.getenv("SIMULATION", "0"))):
-      self.ignore_alive = services
-      self.ignore_average_freq = services
+
+    self.simulation = bool(int(os.getenv("SIMULATION", "0")))
 
     # if freq and poll aren't specified, assume the max to be conservative
     assert frequency is None or poll is None, "Do not specify 'frequency' - frequency of the polled service will be used."
@@ -241,7 +240,7 @@ def update_msgs(self, cur_time: float, msgs: List[capnp.lib.capnp._DynamicStruct
       self.valid[s] = msg.valid
 
     for s in self.data:
-      if SERVICE_LIST[s].frequency > 1e-5:
+      if SERVICE_LIST[s].frequency > 1e-5 and not self.simulation:
         # alive if delay is within 10x the expected frequency
         self.alive[s] = (cur_time - self.recv_time[s]) < (10. / SERVICE_LIST[s].frequency)
 
@@ -261,7 +260,10 @@ def update_msgs(self, cur_time: float, msgs: List[capnp.lib.capnp._DynamicStruct
         self.freq_ok[s] = avg_freq_ok or recent_freq_ok
       else:
         self.freq_ok[s] = True
-        self.alive[s] = True
+        if self.simulation:
+          self.alive[s] = self.seen[s] # alive is defined as seen when simulation flag set
+        else:
+          self.alive[s] = True
 
   def all_alive(self, service_list: Optional[List[str]] = None) -> bool:
     if service_list is None: