diff --git a/lib/i18n.rb b/lib/i18n.rb
index 54008836..297a6255 100644
--- a/lib/i18n.rb
+++ b/lib/i18n.rb
@@ -293,6 +293,10 @@ def enforce_available_locales!(locale)
       end
     end
 
+    def available_locales_initialized?
+      config.available_locales_initialized?
+    end
+
   private
 
     # Any exceptions thrown in translate will be sent to the @@exception_handler
diff --git a/lib/i18n/backend/simple.rb b/lib/i18n/backend/simple.rb
index 00a887b4..ce690484 100644
--- a/lib/i18n/backend/simple.rb
+++ b/lib/i18n/backend/simple.rb
@@ -29,6 +29,11 @@ def initialized?
         # translations will be overwritten by new ones only at the deepest
         # level of the hash.
         def store_translations(locale, data, options = {})
+          if I18n.available_locales_initialized? &&
+            !I18n.available_locales.include?(locale.to_sym) &&
+            !I18n.available_locales.include?(locale.to_s)
+            return data
+          end
           locale = locale.to_sym
           translations[locale] ||= {}
           data = data.deep_symbolize_keys
diff --git a/lib/i18n/config.rb b/lib/i18n/config.rb
index fa16667f..b3736896 100644
--- a/lib/i18n/config.rb
+++ b/lib/i18n/config.rb
@@ -57,6 +57,11 @@ def available_locales=(locales)
       @@available_locales = nil if @@available_locales.empty?
       @@available_locales_set = nil
     end
+    
+    # Returns true if the available_locales have been initialized
+    def available_locales_initialized?
+      ( !!defined?(@@available_locales) && !!@@available_locales )
+    end
 
     # Clears the available locales set so it can be recomputed again after I18n
     # gets reloaded.
diff --git a/test/backend/simple_test.rb b/test/backend/simple_test.rb
index 4d0c447f..c24ff753 100644
--- a/test/backend/simple_test.rb
+++ b/test/backend/simple_test.rb
@@ -70,6 +70,14 @@ def setup
     assert_equal Hash[:'en', {:foo => {:bar => 'bar', :baz => 'baz'}}], translations
   end
 
+  test "simple store_translations: do not store translations for locales not explicitly marked as available" do
+    I18n.available_locales = [:en, :es]
+    store_translations(:fr, :foo => {:bar => 'barfr', :baz => 'bazfr'})
+    store_translations(:es, :foo => {:bar => 'bares', :baz => 'bazes'})
+    assert_nil translations[:fr]
+    assert_equal Hash[:foo, {:bar => 'bares', :baz => 'bazes'}], translations[:es]
+  end
+
   # reloading translations
 
   test "simple reload_translations: unloads translations" do