diff --git a/client/src/pages/auth-page.tsx b/client/src/pages/auth-page.tsx
index 4f04d26..a78f9c8 100644
--- a/client/src/pages/auth-page.tsx
+++ b/client/src/pages/auth-page.tsx
@@ -30,6 +30,7 @@ const registerSchema = z.object({
 export default function AuthPage() {
   const { user, loginMutation, registerMutation } = useAuth();
   const { theme } = useTheme();
+  const { organizations, isLoading: orgsLoading } = useOrganization();
 
   const loginForm = useForm<z.infer<typeof loginSchema>>({
     resolver: zodResolver(loginSchema),
@@ -202,6 +203,34 @@ export default function AuthPage() {
                         </FormItem>
                       )}
                     />
+                    <FormField
+                      control={registerForm.control}
+                      name="organizationId"
+                      render={({ field }) => (
+                        <FormItem>
+                          <FormLabel>Organization</FormLabel>
+                          <FormControl>
+                            <Select
+                              disabled={orgsLoading}
+                              onValueChange={(value) => field.onChange(parseInt(value))}
+                              value={field.value?.toString() || ""}
+                            >
+                              <SelectTrigger>
+                                <SelectValue placeholder="Select an organization (optional)" />
+                              </SelectTrigger>
+                              <SelectContent>
+                                {organizations.map((org) => (
+                                  <SelectItem key={org.id} value={org.id.toString()}>
+                                    {org.name}
+                                  </SelectItem>
+                                ))}
+                              </SelectContent>
+                            </Select>
+                          </FormControl>
+                          <FormMessage />
+                        </FormItem>
+                      )}
+                    />
                     <Button 
                       type="submit" 
                       className="w-full" 
diff --git a/server/storage.ts b/server/storage.ts
index 1e3d25b..b35c1a5 100644
--- a/server/storage.ts
+++ b/server/storage.ts
@@ -147,7 +147,16 @@ export class MemStorage implements IStorage {
   async createUser(user: InsertUser): Promise<User> {
     const id = this.userIdCounter++;
     const createdAt = new Date();
-    const newUser: User = { id, ...user, createdAt };
+    const newUser: User = { 
+      id, 
+      username: user.username,
+      password: user.password,
+      email: user.email,
+      fullName: user.fullName || null,
+      role: user.role || 'user',
+      organizationId: user.organizationId || null,
+      createdAt
+    };
     this.usersMap.set(id, newUser);
     return newUser;
   }
@@ -177,7 +186,12 @@ export class MemStorage implements IStorage {
   async createOrganization(org: InsertOrganization): Promise<Organization> {
     const id = this.orgIdCounter++;
     const createdAt = new Date();
-    const newOrg: Organization = { id, ...org, createdAt };
+    const newOrg: Organization = {
+      id,
+      name: org.name,
+      isActive: org.isActive ?? true,
+      createdAt
+    };
     this.orgsMap.set(id, newOrg);
     return newOrg;
   }
@@ -213,7 +227,15 @@ export class MemStorage implements IStorage {
     const id = this.domainIdCounter++;
     const createdAt = new Date();
     const lastUpdated = new Date();
-    const newDomain: Domain = { id, ...domain, lastUpdated, createdAt };
+    const newDomain: Domain = { 
+      id,
+      name: domain.name,
+      organizationId: domain.organizationId,
+      providerId: domain.providerId,
+      isActive: domain.isActive ?? true,
+      lastUpdated,
+      createdAt
+    };
     this.domainsMap.set(id, newDomain);
     return newDomain;
   }