diff --git a/tidy3d/components/simulation.py b/tidy3d/components/simulation.py
index d4aec37fea..1093886338 100644
--- a/tidy3d/components/simulation.py
+++ b/tidy3d/components/simulation.py
@@ -100,12 +100,13 @@ class Simulation(Box):  # pylint:disable=too-many-public-methods
         units=MICROMETER,
     )
 
-    run_time: pydantic.PositiveFloat = pydantic.Field(
-        ...,
+    run_time: pydantic.NonNegativeFloat = pydantic.Field(
+        0.0,
         title="Run Time",
         description="Total electromagnetic evolution time in seconds. "
         "Note: If simulation 'shutoff' is specified, "
-        "simulation will terminate early when shutoff condition met.",
+        "simulation will terminate early when shutoff condition met. "
+        "Must be set > 0 before running Simulation on our servers.",
         units=SECOND,
     )
 
@@ -468,10 +469,11 @@ def _plane_wave_homogeneous(cls, val, values):
 
     """ Pre submit validation (before web.upload()) """
 
-    def validate_contents(self) -> None:
-        """Validate the fully initialized simulation is within allowed limits."""
+    def validate_pre_upload(self) -> None:
+        """Validate the fully initialized simulation is ok for upload to our servers."""
         self._validate_size()
         self._validate_monitor_size()
+        self._validate_run_time()
 
     def _validate_size(self) -> None:
         """Ensures the simulation is within size limits before simulation is uploaded."""
@@ -516,6 +518,15 @@ def _validate_monitor_size(self) -> None:
                 f"a maximum of {MAX_MONITOR_DATA_SIZE_BYTES:.2e} are allowed."
             )
 
+    def _validate_run_time(self) -> None:
+        """Ensures that the simulation run time is > 0."""
+
+        if not self.run_time > 0:
+            raise SetupError(
+                "The `Simulation.run_time` parameter was left at its default value of 0.0. "
+                "For running a simulation on our servers it must be set to > 0.0."
+            )
+
     """ Accounting """
 
     @property
diff --git a/tidy3d/web/webapi.py b/tidy3d/web/webapi.py
index 2babbfeff9..6458099174 100644
--- a/tidy3d/web/webapi.py
+++ b/tidy3d/web/webapi.py
@@ -428,7 +428,7 @@ def _upload_task(  # pylint:disable=too-many-locals,too-many-arguments
 ) -> TaskId:
     """upload with all kwargs exposed"""
 
-    simulation.validate_contents()
+    simulation.validate_pre_upload()
 
     json_string = simulation._json_string()  # pylint:disable=protected-access
     data = {