diff --git a/src/FactorioTools/OilField/Planner.cs b/src/FactorioTools/OilField/Planner.cs
index 63c9d244..9d47d8cd 100644
--- a/src/FactorioTools/OilField/Planner.cs
+++ b/src/FactorioTools/OilField/Planner.cs
@@ -106,6 +106,11 @@ private static (Context Context, OilFieldPlanSummary Summary) Execute(
 
         var finalPumpjackCount = context.CenterToTerminals.Count;
 
+        if (finalPumpjackCount != initialPumpjackCount)
+        {
+            throw new FactorioToolsException("The initial number of pumpjacks does not match the final pumpjack count.");
+        }
+
         var planSummary = new OilFieldPlanSummary(
             initialPumpjackCount - finalPumpjackCount,
             selectedPlans,