diff --git a/backend/capellacollab/settings/modelsources/t4c/repositories/models.py b/backend/capellacollab/settings/modelsources/t4c/repositories/models.py
index e15201c16..ebe644770 100644
--- a/backend/capellacollab/settings/modelsources/t4c/repositories/models.py
+++ b/backend/capellacollab/settings/modelsources/t4c/repositories/models.py
@@ -44,7 +44,9 @@ class DatabaseT4CRepository(database.Base):
 
 
 class CreateT4CRepository(pydantic.BaseModel):
-    name: str
+    name: str = pydantic.Field(
+        pattern="^[-a-zA-Z0-9_]+$", examples=["testrepo"]
+    )
 
 
 class T4CRepositoryStatus(str, enum.Enum):
diff --git a/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.html b/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.html
index 7249ff4ec..5e03c7df2 100644
--- a/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.html
+++ b/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.html
@@ -35,9 +35,12 @@
         <mat-form-field appearance="fill">
           <mat-label>Repository</mat-label>
           <input matInput formControlName="t4cRepositoryName" />
-          <mat-error *ngIf="t4cRepositoryNameControl.errors?.uniqueName"
-            >Repository already exists</mat-error
-          >
+          <mat-error *ngIf="t4cRepositoryNameControl.errors?.uniqueName">
+            Repository already exists
+          </mat-error>
+          <mat-error *ngIf="t4cRepositoryNameControl.errors?.pattern">
+            The following characters are allowed: A-Z, a-z, 0-9, _, -
+          </mat-error>
         </mat-form-field>
       </fieldset>
 
diff --git a/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.ts b/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.ts
index 30e947c32..83960f487 100644
--- a/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.ts
+++ b/frontend/src/app/projects/models/model-source/t4c/create-t4c-model-new-repository/create-t4c-model-new-repository.component.ts
@@ -43,8 +43,13 @@ export class CreateT4cModelNewRepositoryComponent implements OnInit {
     t4cInstanceId: new FormControl<number | null>(null, Validators.required),
     t4cRepositoryName: new FormControl<string | null>(
       { value: null, disabled: true },
-      Validators.required,
-      this.t4cRepoService.asyncNameValidator(),
+      {
+        validators: [
+          Validators.required,
+          Validators.pattern(/^[-a-zA-Z0-9_]+$/),
+        ],
+        asyncValidators: this.t4cRepoService.asyncNameValidator(),
+      },
     ),
     t4cProjectName: new FormControl<string | null>(
       { value: null, disabled: true },