diff --git a/apps/edr-freight-api/src/modules/train-scheduling/train-capacity.util.ts b/apps/edr-freight-api/src/modules/train-scheduling/train-capacity.util.ts
index 463ae7ea8..3e4fab0d3 100644
--- a/apps/edr-freight-api/src/modules/train-scheduling/train-capacity.util.ts
+++ b/apps/edr-freight-api/src/modules/train-scheduling/train-capacity.util.ts
@@ -253,12 +253,18 @@ export function minLocomotiveLimits(
     maxTrainLengthMeters: Math.min(
       ...locomotives.map((l) => num(l.maxTrainLengthMeters, Infinity) || Infinity),
     ),
-    // Weakest locomotive's tolerance governs the set, same as its caps.
-    overageToleranceTons: Math.min(...locomotives.map((l) => num(l.overageToleranceTons))),
-    overageToleranceMeters: Math.min(...locomotives.map((l) => num(l.overageToleranceMeters))),
+    // Weakest CONFIGURED tolerance governs the set — a locomotive with no
+    // tolerance set has no opinion, it does not zero out the others.
+    overageToleranceTons: minConfigured(locomotives.map((l) => l.overageToleranceTons)),
+    overageToleranceMeters: minConfigured(locomotives.map((l) => l.overageToleranceMeters)),
   };
 }
 
+function minConfigured(values: Array<number | string | null | undefined>): number {
+  const configured = values.filter((v) => v != null).map((v) => num(v));
+  return configured.length ? Math.min(...configured) : 0;
+}
+
 /** Per-booking train length from wagon count and freight-specific wagon type length. */
 export function bookingTrainLengthMeters(
   freightType: string | null | undefined,