diff --git a/Library/Homebrew/locale.rb b/Library/Homebrew/locale.rb
index d918e2a2a4..c430d11b64 100644
--- a/Library/Homebrew/locale.rb
+++ b/Library/Homebrew/locale.rb
@@ -2,9 +2,9 @@ class Locale
   class ParserError < StandardError
   end
 
-  LANGUAGE_REGEX = /(?:[a-z]{2,3})/    # ISO 639-1 or ISO 639-2
-  REGION_REGEX   = /(?:[A-Z]{2})/      # ISO 3166-1
-  SCRIPT_REGEX   = /(?:[A-Z][a-z]{3})/ # ISO 15924
+  LANGUAGE_REGEX = /(?:[a-z]{2,3})/     # ISO 639-1 or ISO 639-2
+  REGION_REGEX   = /(?:[A-Z]{2}|\d{3})/ # ISO 3166-1 or UN M.49
+  SCRIPT_REGEX   = /(?:[A-Z][a-z]{3})/  # ISO 15924
 
   LOCALE_REGEX = /\A((?:#{LANGUAGE_REGEX}|#{REGION_REGEX}|#{SCRIPT_REGEX})(?:\-|$)){1,3}\Z/
 
diff --git a/Library/Homebrew/test/locale_spec.rb b/Library/Homebrew/test/locale_spec.rb
index 9e4d09e837..9c684f0e7f 100644
--- a/Library/Homebrew/test/locale_spec.rb
+++ b/Library/Homebrew/test/locale_spec.rb
@@ -9,6 +9,10 @@ describe Locale do
       expect(described_class.parse("zh-CN-Hans")).to eql(described_class.new("zh", "CN", "Hans"))
     end
 
+    it "correctly parses a string with a UN M.49 region code" do
+      expect(described_class.parse("es-419")).to eql(described_class.new("es", "419", nil))
+    end
+
     context "raises a ParserError when given" do
       it "an empty string" do
         expect { described_class.parse("") }.to raise_error(Locale::ParserError)