diff --git a/server/src/modules/electoralOffice.ts b/server/src/modules/electoralOffice.ts
index 609fb9ac..06101597 100644
--- a/server/src/modules/electoralOffice.ts
+++ b/server/src/modules/electoralOffice.ts
@@ -137,7 +137,7 @@ export async function createVote(
     });
 }
 
-export async function deleteVote(ctx: IAppContext, id: string) {
+export async function deleteVote(ctx: IAppContext, id: string): Promise<void> {
     const { knex, session } = ctx;
     assertRole(ctx, session.userSignature, "POLITICS");
     return knex.transaction(async (trx) => {
diff --git a/server/src/util/misc.ts b/server/src/util/misc.ts
index 5ae25aa0..682e732e 100644
--- a/server/src/util/misc.ts
+++ b/server/src/util/misc.ts
@@ -109,7 +109,7 @@ export const compute = <T>(f: () => T): T => f();
 /** Apply a function if value is not null */
 export const mapNullableC =
     <T, U>(f: (_x: T) => U) =>
-    (x: TNullable<T>) =>
+    (x: TNullable<T>): TNullable<U> =>
         isNull(x) ? null : f(x);
 
 /* * Haskell-style logging functions * */
diff --git a/types.ts b/types.ts
index c634f3fa..5eee24e4 100644
--- a/types.ts
+++ b/types.ts
@@ -213,7 +213,7 @@ export function inOperator<K extends PropertyKey, O>(
     key: K,
     obj: O
 ): obj is O & Record<K, unknown> {
-    return key in obj;
+    return typeof obj === "object" && obj !== null && key in obj;
 }
 
 export function checkPropertyType<K extends PropertyKey, O, T>(