diff --git a/src/aeros_simulation/schema.py b/src/aeros_simulation/schema.py
index a5b3d7f..07bf141 100644
--- a/src/aeros_simulation/schema.py
+++ b/src/aeros_simulation/schema.py
@@ -72,7 +72,7 @@ class SimulationCalc(BaseModel):
     contribution: Optional[float] = 0
     criticality: Optional[float]
     contribution_factor: Optional[float]
-    sof: float
+    sof: Optional[float]
 
 class SimulationPlot(BaseModel):
     id: UUID