diff --git a/src/resolvers/ParkingStructureResolvers.ts b/src/resolvers/ParkingStructureResolvers.ts
index 6ab6dfc..dc995c6 100644
--- a/src/resolvers/ParkingStructureResolvers.ts
+++ b/src/resolvers/ParkingStructureResolvers.ts
@@ -1,6 +1,7 @@
 import { Resolvers } from "../generated/graphql";
 import { ServerContext } from "../ServerContext";
 import { HistoricalParkingAverageQueryArguments } from "../repositories/parking/ParkingGetterRepository";
+import { GraphQLError } from "graphql/error";
 
 export const ParkingStructureResolvers: Resolvers<ServerContext> = {
   ParkingStructure: {
@@ -8,7 +9,11 @@ export const ParkingStructureResolvers: Resolvers<ServerContext> = {
       const system = contextValue.findSystemById(parent.systemId);
 
       if (!args.input?.intervalMs) {
-        return null;
+        throw new GraphQLError('No interval provided', {
+          extensions: {
+            code: 'BAD_USER_INPUT',
+          },
+        });
       }
       const historicalParkingAverageQueryArguments: HistoricalParkingAverageQueryArguments = {
         from: new Date(args.input.from),
@@ -17,7 +22,11 @@ export const ParkingStructureResolvers: Resolvers<ServerContext> = {
       }
       if (Number.isNaN(historicalParkingAverageQueryArguments.from.getTime()
         || Number.isNaN(historicalParkingAverageQueryArguments.to.getTime()))) {
-        return null;
+        throw new GraphQLError('One or more invalid dates provided', {
+          extensions: {
+            code: 'BAD_USER_INPUT',
+          },
+        });
       }
 
       const parkingAverages = await system?.parkingRepository?.getHistoricalAveragesOfParkingStructureCounts(parent.id, historicalParkingAverageQueryArguments);