diff --git a/babel/numbers.py b/babel/numbers.py
index 624e8d61e..e39a13d37 100644
--- a/babel/numbers.py
+++ b/babel/numbers.py
@@ -774,6 +774,8 @@ def format_currency(
                                           locale=locale, currency_digits=currency_digits,
                                           decimal_quantization=decimal_quantization, group_separator=group_separator,
                                           numbering_system=numbering_system)
+    if locale is None:
+        locale = default_locale()
     locale = Locale.parse(locale)
     if format:
         pattern = parse_pattern(format)
diff --git a/tests/test_numbers.py b/tests/test_numbers.py
index 106b83edf..a1d041c37 100644
--- a/tests/test_numbers.py
+++ b/tests/test_numbers.py
@@ -485,6 +485,11 @@ def test_format_currency():
     assert (numbers.format_currency(0, 'USD', locale='es_AR')
             == 'US$0,00')          # other
 
+def test_format_currency_with_none_locale():
+    assert (numbers.format_currency(0, "USD", locale=None) 
+            == "0,00\xa0$US")
+    assert (numbers.format_currency(1099.98, "EUR", locale=None) 
+            == "1\u202f099,98\xa0€")
 
 def test_format_currency_format_type():
     assert (numbers.format_currency(1099.98, 'USD', locale='en_US',