diff --git a/backend/src/services/rating-service.ts b/backend/src/services/rating-service.ts
index 298efbc..d02a281 100644
--- a/backend/src/services/rating-service.ts
+++ b/backend/src/services/rating-service.ts
@@ -235,17 +235,6 @@ export class RatingService implements IRatingService {
       throw new ForbiddenError("Only admitted users may rate projects");
     }
 
-    // TODO only users in a team are allowed to vote. Prevent them from
-    //  leaving their team to vote for themselves. However, they could leave
-    //  their team and create a new one. So they need to be in a team that has
-    //  been created before the rating started. I don't track the timestamp yet...
-    //  Prevent teams from changing once rating starts is the best bet. Use the
-    //  existing switch and prevent changes, add some text to the settings page that
-    //  this is the case to avoid confusion. Still, people could join a second team
-    //  before voting starts, in order to vote for their own project. I don't think
-    //  it is possible to avoid this situation. It needs to be prohibited via the
-    //  rules and it needs a way to check if this happened, but the ratings are
-    //  anonymous. HOORAY. Or we allow people to rate their own project after all.
     if (user.team == null) {
       throw new ForbiddenError("You need to be part of a team to vote");
     }
diff --git a/backend/src/services/team-service.ts b/backend/src/services/team-service.ts
index 687dea8..66b90a3 100644
--- a/backend/src/services/team-service.ts
+++ b/backend/src/services/team-service.ts
@@ -248,6 +248,17 @@ export class TeamService implements ITeamService {
       );
     }
 
+    if (user.team != null) {
+      const oldTeam = await this._teams.findOne({
+        where: { id: user.team.id },
+        relations: ["users", "requests", "owner"],
+      });
+
+      if (oldTeam?.owner?.id === user.id) {
+        throw new Error("Make someone else owner of your other team first");
+      }
+    }
+
     await this._users.save({
       ...user,
       teamRequest: team,
diff --git a/backend/test/services/team-service.spec.ts b/backend/test/services/team-service.spec.ts
index 114a9dc..6d59c61 100644
--- a/backend/test/services/team-service.spec.ts
+++ b/backend/test/services/team-service.spec.ts
@@ -88,6 +88,23 @@ describe("TeamService", () => {
     });
   });
 
+  describe("requestToJoinTeam", () => {
+    it("throws when the requester is owner of a team", async () => {
+      expect.assertions(1);
+
+      const requestingUser = await userRepo.save(makeUser("req@test.com"));
+      const createdTeam = await teamService.createTeam(
+        makeTeam(),
+        requestingUser,
+      );
+      await userRepo.save({ ...requestingUser, team: createdTeam });
+
+      await expect(
+        teamService.requestToJoinTeam(createdTeam.id, requestingUser),
+      ).rejects.toThrow("Make someone else owner of your other team first");
+    });
+  });
+
   describe("acceptUserToTeam", () => {
     it("throws when the requester is neither owner nor admin", async () => {
       expect.assertions(1);
diff --git a/frontend/src/components/base/notification.tsx b/frontend/src/components/base/notification.tsx
index 473cc5c..896cb14 100644
--- a/frontend/src/components/base/notification.tsx
+++ b/frontend/src/components/base/notification.tsx
@@ -9,6 +9,8 @@ const NotificationContainer = styled(NonGrowingFlexContainer)`
   right: -5rem;
   opacity: 0;
 
+  pointer-events: none;
+
   padding: 0.75rem 1.5rem;
 
   text-transform: uppercase;
diff --git a/frontend/src/components/pages/rating-form.tsx b/frontend/src/components/pages/rating-form.tsx
index e229c5f..139b150 100644
--- a/frontend/src/components/pages/rating-form.tsx
+++ b/frontend/src/components/pages/rating-form.tsx
@@ -18,6 +18,8 @@ interface IRatingFormProps {
   project: ProjectDTO;
 }
 
+const NOT_RATED = -1;
+
 /**
  * Component that allows users to submit and edit ratings for projects.
  * Only for one criterion, use multiple of this to cover all of them.
@@ -32,7 +34,9 @@ export const RatingForm = ({
 
   const { showNotification } = useNotificationContext();
 
-  const [ratingValue, setRatingValue] = useState<number>(rating?.rating || 3);
+  const [ratingValue, setRatingValue] = useState<number>(
+    rating?.rating || NOT_RATED,
+  );
   const [isSubmitting, setIsSubmitting] = useState(false);
 
   React.useEffect(() => {
@@ -42,6 +46,10 @@ export const RatingForm = ({
   }, [rating]);
 
   const handleSubmit = async () => {
+    if (ratingValue === NOT_RATED) {
+      return;
+    }
+
     setIsSubmitting(true);
 
     await api.createRating({
@@ -64,6 +72,13 @@ export const RatingForm = ({
           value={ratingValue?.toString()}
           onChange={(e) => setRatingValue(parseInt(e.target.value, 10))}
         >
+          <FormControlLabel
+            key="hidden"
+            value={NOT_RATED.toString()}
+            control={<Radio disabled={isSubmitting} />}
+            label=""
+            style={{ display: "none" }}
+          />
           {[1, 2, 3, 4, 5].map((value) => (
             <FormControlLabel
               key={value.toString()}
diff --git a/frontend/src/components/pages/read-only-team.tsx b/frontend/src/components/pages/read-only-team.tsx
index d72d44c..8449164 100644
--- a/frontend/src/components/pages/read-only-team.tsx
+++ b/frontend/src/components/pages/read-only-team.tsx
@@ -25,12 +25,19 @@ export const ReadOnlyTeam = ({ team }: { team: TeamResponseDTO }) => {
 
   const { forcePerformRequest: sendRequestToJoin } = useApi(
     async (apiClient, wasTriggeredManually) => {
-      if (wasTriggeredManually) {
+      if (!wasTriggeredManually) {
+        return false;
+      }
+
+      try {
         await apiClient.requestToJoinTeam(Number(params.get("id")));
         showNotification("Request sent");
         return true;
+      } catch (error) {
+        if (error instanceof Error) {
+          showNotification(error.message);
+        }
       }
-      return false;
     },
     [],
   );