diff --git a/lib/fog/core/credentials.rb b/lib/fog/core/credentials.rb
index e62bc9a79..68a1602a4 100644
--- a/lib/fog/core/credentials.rb
+++ b/lib/fog/core/credentials.rb
@@ -45,6 +45,11 @@ module Fog
     end
   end
 
+  # @return [Hash] The newly assigned credentials
+  def self.credentials=(new_credentials)
+    @credentials = new_credentials
+  end
+
   def self.symbolize_credentials(args)
     if args.is_a? Hash
       Hash[ *args.collect do |key, value|
diff --git a/tests/helpers/mock_helper.rb b/tests/helpers/mock_helper.rb
index 260fe47c1..000ff0e71 100644
--- a/tests/helpers/mock_helper.rb
+++ b/tests/helpers/mock_helper.rb
@@ -8,7 +8,7 @@ end
 
 # if in mocked mode, fill in some fake credentials for us
 if Fog.mock?
-  Fog.instance_variable_set(:@credentials, {
+  Fog.credentials = {
     :aws_access_key_id                => 'aws_access_key_id',
     :aws_secret_access_key            => 'aws_secret_access_key',
     :bluebox_api_key                  => 'bluebox_api_key',
@@ -57,5 +57,5 @@ if Fog.mock?
     :vsphere_username                 => 'apiuser',
     :vsphere_password                 => 'apipassword',
     :vsphere_expected_pubkey_hash     => 'abcdef1234567890'
-  })
+  }
 end