diff --git a/src/SupabaseClient.ts b/src/SupabaseClient.ts
index f6649bf86..c48e0ad69 100644
--- a/src/SupabaseClient.ts
+++ b/src/SupabaseClient.ts
@@ -62,13 +62,13 @@ export default class SupabaseClient {
     if (!supabaseUrl) throw new Error('supabaseUrl is required.')
     if (!supabaseKey) throw new Error('supabaseKey is required.')
 
-    supabaseUrl = stripTrailingSlash(supabaseUrl)
-
+    const _supabaseUrl = stripTrailingSlash(supabaseUrl)
     const settings = { ...DEFAULT_OPTIONS, ...options }
-    this.restUrl = `${supabaseUrl}/rest/v1`
-    this.realtimeUrl = `${supabaseUrl}/realtime/v1`.replace('http', 'ws')
-    this.authUrl = `${supabaseUrl}/auth/v1`
-    this.storageUrl = `${supabaseUrl}/storage/v1`
+
+    this.restUrl = `${_supabaseUrl}/rest/v1`
+    this.realtimeUrl = `${_supabaseUrl}/realtime/v1`.replace('http', 'ws')
+    this.authUrl = `${_supabaseUrl}/auth/v1`
+    this.storageUrl = `${_supabaseUrl}/storage/v1`
     this.schema = settings.schema
     this.multiTab = settings.multiTab
     this.fetch = settings.fetch
diff --git a/src/lib/helpers.ts b/src/lib/helpers.ts
index aa90ffc02..3670ff1bb 100644
--- a/src/lib/helpers.ts
+++ b/src/lib/helpers.ts
@@ -8,7 +8,7 @@ export function uuid() {
   })
 }
 
-export function stripTrailingSlash(url: string) {
+export function stripTrailingSlash(url: string): string {
   return url.replace(/\/$/, '')
 }
 
diff --git a/test/helper.test.ts b/test/helper.test.ts
new file mode 100644
index 000000000..ba422297d
--- /dev/null
+++ b/test/helper.test.ts
@@ -0,0 +1,13 @@
+import { stripTrailingSlash } from '../src/lib/helpers'
+
+test('Strip trailing slash from URL', () => {
+  const URL = 'http://localhost:3000/'
+  const expectedURL = URL.slice(0, -1)
+  expect(stripTrailingSlash(URL)).toBe(expectedURL)
+})
+
+test('Return the original URL if there is no slash at the end', () => {
+  const URL = 'http://localhost:3000'
+  const expectedURL = URL
+  expect(stripTrailingSlash(URL)).toBe(expectedURL)
+})