diff --git a/src/octoprint/util/comm.py b/src/octoprint/util/comm.py
index 3653a108..562a3b3a 100644
--- a/src/octoprint/util/comm.py
+++ b/src/octoprint/util/comm.py
@@ -1195,7 +1195,7 @@ class MachineCom(object):
 
 				# temperature processing
 				elif ' T:' in line or line.startswith('T:') or ' T0:' in line or line.startswith('T0:') or ((' B:' in line or line.startswith('B:')) and not 'A:' in line):
-					if not disable_external_heatup_detection and not line.strip().startswith("ok") and not self._heating:
+					if not disable_external_heatup_detection and not line.strip().startswith("ok") and not self._heating and self._firmwareInfoReceived:
 						self._logger.debug("Externally triggered heatup detected")
 						self._heating = True
 						self._heatupWaitStartTime = time.time()