diff --git a/frontend/src/queries/assignments.ts b/frontend/src/queries/assignments.ts
index ddfe0bc4..8dd2912b 100644
--- a/frontend/src/queries/assignments.ts
+++ b/frontend/src/queries/assignments.ts
@@ -29,7 +29,7 @@ export async function invalidateAllAssignmentKeys(queryClient: QueryClient, clas
         "assignment-questions",
     ];
 
-    for (let key of keys) {
+    for (const key of keys) {
         const queryKey = [key, classid, assignmentNumber].filter(arg => arg !== undefined);
         await queryClient.invalidateQueries({ queryKey: queryKey });
     }
diff --git a/frontend/src/queries/classes.ts b/frontend/src/queries/classes.ts
index 66be4acf..e4ecfcb1 100644
--- a/frontend/src/queries/classes.ts
+++ b/frontend/src/queries/classes.ts
@@ -38,7 +38,7 @@ export async function invalidateAllClassKeys(queryClient: QueryClient, classid?:
         "class-assignments",
     ];
 
-    for (let key of keys) {
+    for (const key of keys) {
         const queryKey = [key, classid].filter(arg => arg !== undefined);
         await queryClient.invalidateQueries({ queryKey: queryKey });
     }
@@ -109,7 +109,7 @@ export function useClassStudentsQuery(
 ): UseQueryReturnType<StudentsResponse, Error> {
     return useQuery({
         queryKey: computed(() => classStudentsKey(toValue(id)!, toValue(full))),
-        queryFn: async () => classController.getStudents(toValue(id)!, toValue(full)!),
+        queryFn: async () => classController.getStudents(toValue(id)!, toValue(full)),
         enabled: () => Boolean(toValue(id)),
     })
 }
@@ -146,7 +146,7 @@ export function useClassTeachersQuery(
 ): UseQueryReturnType<StudentsResponse, Error> {
     return useQuery({
         queryKey: computed(() => classTeachersKey(toValue(id)!, toValue(full))),
-        queryFn: async () => classController.getTeachers(toValue(id)!, toValue(full)!),
+        queryFn: async () => classController.getTeachers(toValue(id)!, toValue(full)),
         enabled: () => Boolean(toValue(id)),
     });
 }
@@ -183,7 +183,7 @@ export function useClassTeacherInvitationsQuery(
 ): UseQueryReturnType<StudentsResponse, Error> {
     return useQuery({
         queryKey: computed(() => classTeacherInvitationsKey(toValue(id)!, toValue(full))),
-        queryFn: async () => classController.getTeacherInvitations(toValue(id)!, toValue(full)!),
+        queryFn: async () => classController.getTeacherInvitations(toValue(id)!, toValue(full)),
         enabled: () => Boolean(toValue(id)),
     });
 }
@@ -194,7 +194,7 @@ export function useClassAssignmentsQuery(
 ): UseQueryReturnType<StudentsResponse, Error> {
     return useQuery({
         queryKey: computed(() => classAssignmentsKey(toValue(id)!, toValue(full))),
-        queryFn: async () => classController.getAssignments(toValue(id)!, toValue(full)!),
+        queryFn: async () => classController.getAssignments(toValue(id)!, toValue(full)),
         enabled: () => Boolean(toValue(id)),
     });
 }
\ No newline at end of file
diff --git a/frontend/src/queries/groups.ts b/frontend/src/queries/groups.ts
index dbe4bcd7..7ed67cbc 100644
--- a/frontend/src/queries/groups.ts
+++ b/frontend/src/queries/groups.ts
@@ -33,7 +33,7 @@ export async function invalidateAllGroupKeys(
         "group-questions",
     ];
 
-    for (let key of keys) {
+    for (const key of keys) {
         const queryKey = [key, classid, assignmentNumber, groupNumber].filter(arg => arg !== undefined);
         await queryClient.invalidateQueries({ queryKey: queryKey });
     }
diff --git a/frontend/src/queries/submissions.ts b/frontend/src/queries/submissions.ts
index 743b1d09..5360afaf 100644
--- a/frontend/src/queries/submissions.ts
+++ b/frontend/src/queries/submissions.ts
@@ -21,7 +21,7 @@ export async function invalidateAllSubmissionKeys(
         "submission",
     ];
 
-    for (let key of keys) {
+    for (const key of keys) {
         const queryKey = [key, classid, assignmentNumber, groupNumber, submissionNumber].filter(arg => arg !== undefined);
         await queryClient.invalidateQueries({ queryKey: queryKey });
     }