diff --git a/src/client/includes/formatters.ts b/src/client/includes/formatters.ts
index 7040289..7a50def 100644
--- a/src/client/includes/formatters.ts
+++ b/src/client/includes/formatters.ts
@@ -27,7 +27,7 @@ export const getNumberFormatter: MemoizedIntlFormatter<
   }
 
   if (format) {
-    options = getIntlFormatterOptions('number', format) || {}
+    options = getIntlFormatterOptions('number', format)
   }
 
   return new Intl.NumberFormat(locale, options)
diff --git a/src/client/index.ts b/src/client/index.ts
index 437a4bf..87b3df6 100644
--- a/src/client/index.ts
+++ b/src/client/index.ts
@@ -8,13 +8,8 @@ export function defineMessages(i: Record<string, MessageObject>) {
   return i
 }
 
-export function waitLocale(locale: string) {
-  return flush(
-    locale ||
-      getCurrentLocale() ||
-      getOptions().initialLocale ||
-      getOptions().fallbackLocale
-  )
+export function waitLocale(locale?: string) {
+  return flush(locale || getCurrentLocale() || getOptions().initialLocale)
 }
 
 export { init } from './configs'
diff --git a/test/client/includes/formatters.test.ts b/test/client/includes/formatters.test.ts
index 17d5723..9027f71 100644
--- a/test/client/includes/formatters.test.ts
+++ b/test/client/includes/formatters.test.ts
@@ -12,19 +12,26 @@ beforeEach(() => {
 
 describe('number formatter', () => {
   const number = 123123
-  test('should format a date according to the current locale', () => {
+
+  test('throws if no locale is set', () => {
+    expect(() => getNumberFormatter().format(number)).toThrow(
+      '[svelte-i18n] A "locale" must be set to format numbers'
+    )
+  })
+
+  test('formats a date according to the current locale', () => {
     init({ fallbackLocale: 'en' })
     expect(getNumberFormatter().format(number)).toBe('123,123')
   })
 
-  test('should format a number according to a locale', () => {
+  test('formats a number according to a locale', () => {
     init({ fallbackLocale: 'en' })
     expect(getNumberFormatter({ locale: 'pt-BR' }).format(number)).toBe(
       '123.123'
     )
   })
 
-  test('should format a number with a custom format', () => {
+  test('formats a number with a custom format', () => {
     init({
       fallbackLocale: 'en',
       formats: require('../../fixtures/formats.json'),
@@ -35,7 +42,7 @@ describe('number formatter', () => {
     )
   })
 
-  test('should format a number with inline options', () => {
+  test('formats a number with inline options', () => {
     init({ fallbackLocale: 'en' })
 
     expect(
@@ -47,16 +54,22 @@ describe('number formatter', () => {
 describe('date formatter', () => {
   const date = new Date(2019, 1, 1)
 
-  test('should format a date according to the current locale', () => {
+  test('throws if no locale is set', () => {
+    expect(() => getDateFormatter().format(date)).toThrow(
+      '[svelte-i18n] A "locale" must be set to format dates'
+    )
+  })
+
+  test('formats a date according to the current locale', () => {
     init({ fallbackLocale: 'en' })
     expect(getDateFormatter().format(date)).toBe('2/1/19')
   })
 
-  test('should format a date according to a locale', () => {
+  test('formats a date according to a locale', () => {
     expect(getDateFormatter({ locale: 'pt-BR' }).format(date)).toBe('01/02/19')
   })
 
-  test('should throw if passed a non-existing format', () => {
+  test('throws if passed a non-existing format', () => {
     init({
       fallbackLocale: 'en',
       formats: require('../../fixtures/formats.json'),
@@ -67,7 +80,7 @@ describe('date formatter', () => {
     ).toThrowError(`[svelte-i18n] Unknown "foo" date format.`)
   })
 
-  test('should format a date with a custom format', () => {
+  test('formats a date with a custom format', () => {
     init({
       fallbackLocale: 'en',
       formats: require('../../fixtures/formats.json'),
@@ -78,7 +91,7 @@ describe('date formatter', () => {
     )
   })
 
-  test('should format a date with inline options', () => {
+  test('formats a date with inline options', () => {
     init({ fallbackLocale: 'en' })
 
     expect(
@@ -90,16 +103,22 @@ describe('date formatter', () => {
 describe('time formatter', () => {
   const time = new Date(2019, 1, 1, 20, 37, 32)
 
-  test('should format a time according to the current locale', () => {
+  test('throws if no locale is set', () => {
+    expect(() => getTimeFormatter().format(time)).toThrow(
+      '[svelte-i18n] A "locale" must be set to format time'
+    )
+  })
+
+  test('formats a time according to the current locale', () => {
     init({ fallbackLocale: 'en' })
     expect(getTimeFormatter().format(time)).toBe('8:37 PM')
   })
 
-  test('should format a time according to a locale', () => {
+  test('formats a time according to a locale', () => {
     expect(getTimeFormatter({ locale: 'pt-BR' }).format(time)).toBe('20:37')
   })
 
-  test('should format a time with a custom format', () => {
+  test('formats a time with a custom format', () => {
     init({
       fallbackLocale: 'en',
       formats: require('../../fixtures/formats.json'),
@@ -110,7 +129,7 @@ describe('time formatter', () => {
     )
   })
 
-  test('should throw if passed a non-existing format', () => {
+  test('throws if passed a non-existing format', () => {
     init({
       fallbackLocale: 'en',
       formats: require('../../fixtures/formats.json'),
@@ -121,7 +140,7 @@ describe('time formatter', () => {
     ).toThrowError(`[svelte-i18n] Unknown "foo" time format.`)
   })
 
-  test('should format a time with inline options', () => {
+  test('formats a time with inline options', () => {
     init({ fallbackLocale: 'en' })
 
     expect(
diff --git a/test/client/index.test.ts b/test/client/index.test.ts
index 1867b05..5da3394 100644
--- a/test/client/index.test.ts
+++ b/test/client/index.test.ts
@@ -1,6 +1,49 @@
-import { defineMessages } from '../../src/client'
+import { defineMessages, waitLocale, register, init } from '../../src/client'
+import { $locale } from '../../src/client/stores/locale'
+import { hasLocaleQueue } from '../../src/client/includes/loaderQueue'
+import {
+  getLocaleDictionary,
+  $dictionary,
+} from '../../src/client/stores/dictionary'
 
 test('defineMessages returns the identity of its first argument', () => {
   const obj = {}
   expect(obj).toBe(defineMessages(obj))
 })
+
+describe('waiting for a locale to load', () => {
+  beforeEach(() => {
+    $dictionary.set({})
+    $locale.set(undefined)
+  })
+
+  test('should wait for a locale queue to be flushed', async () => {
+    register('en', () => Promise.resolve({ foo: 'foo' }))
+    $locale.set('en')
+
+    await waitLocale('en')
+
+    expect(hasLocaleQueue('en')).toBe(false)
+    expect(getLocaleDictionary('en')).toMatchObject({ foo: 'foo' })
+  })
+
+  test('should wait for the current locale queue to be flushed', async () => {
+    register('en', () => Promise.resolve({ foo: 'foo' }))
+    init({ fallbackLocale: 'pt', initialLocale: 'en' })
+
+    await waitLocale()
+
+    expect(hasLocaleQueue('en')).toBe(false)
+    expect(getLocaleDictionary('en')).toMatchObject({ foo: 'foo' })
+  })
+
+  test('should wait for the fallback locale queue to be flushed if initial not set', async () => {
+    register('pt', () => Promise.resolve({ foo: 'foo' }))
+    init({ fallbackLocale: 'pt' })
+
+    await waitLocale()
+
+    expect(hasLocaleQueue('pt')).toBe(false)
+    expect(getLocaleDictionary('pt')).toMatchObject({ foo: 'foo' })
+  })
+})