diff --git a/spec/googleauth/get_application_default_spec.rb b/spec/googleauth/get_application_default_spec.rb
index 2794bc7..d1cf6ba 100644
--- a/spec/googleauth/get_application_default_spec.rb
+++ b/spec/googleauth/get_application_default_spec.rb
@@ -50,12 +50,16 @@ describe '#get_application_default' do
     @original_env_vals = {}
     @credential_vars.each { |var| @original_env_vals[var] = ENV[var] }
     @home = ENV['HOME']
+    @app_data = ENV['APPDATA']
+    @program_data = ENV['ProgramData']
     @scope = 'https://www.googleapis.com/auth/userinfo.profile'
   end
 
   after(:example) do
     @credential_vars.each { |var| ENV[var] = @original_env_vals[var] }
     ENV['HOME'] = @home unless @home == ENV['HOME']
+    ENV['APPDATA'] = @app_data unless @app_data == ENV['APPDATA']
+    ENV['ProgramData'] = @program_data unless @program_data == ENV['ProgramData']
   end
 
   shared_examples 'it cannot load misconfigured credentials' do
@@ -90,7 +94,7 @@ describe '#get_application_default' do
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV[@var_name] = key_path
-        expect(Google::Auth.get_application_default @scope, options)
+        expect(Google::Auth.get_application_default(@scope, options))
           .to_not be_nil
       end
     end
@@ -99,10 +103,12 @@ describe '#get_application_default' do
       ENV.delete(@var_name) unless ENV[@var_name].nil?
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, '.config', WELL_KNOWN_PATH)
+        key_path = File.join(dir, WELL_KNOWN_PATH) if OS.windows?
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV['HOME'] = dir
-        expect(Google::Auth.get_application_default @scope, options)
+        ENV['APPDATA'] = dir
+        expect(Google::Auth.get_application_default(@scope, options))
           .to_not be_nil
       end
     end
@@ -111,10 +117,12 @@ describe '#get_application_default' do
       ENV.delete(@var_name) unless ENV[@var_name].nil?
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, '.config', WELL_KNOWN_PATH)
+        key_path = File.join(dir, WELL_KNOWN_PATH) if OS.windows?
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV['HOME'] = dir
-        expect(Google::Auth.get_application_default nil, options).to_not be_nil
+        ENV['APPDATA'] = dir
+        expect(Google::Auth.get_application_default(nil, options)).to_not be_nil
       end
     end
 
@@ -134,10 +142,12 @@ describe '#get_application_default' do
     it 'succeeds with system default file' do
       ENV.delete(@var_name) unless ENV[@var_name].nil?
       FakeFS do
-        key_path = File.join('/etc/google/auth/', CREDENTIALS_FILE_NAME)
+        ENV['ProgramData'] = '/etc'
+        prefix = OS.windows? ? '/etc/Google/Auth/' : '/etc/google/auth/'
+        key_path = File.join(prefix, CREDENTIALS_FILE_NAME)
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
-        expect(Google::Auth.get_application_default @scope, options)
+        expect(Google::Auth.get_application_default(@scope, options))
           .to_not be_nil
         File.delete(key_path)
       end
@@ -151,7 +161,7 @@ describe '#get_application_default' do
       ENV[CLIENT_SECRET_VAR] = cred_json[:client_secret]
       ENV[REFRESH_TOKEN_VAR] = cred_json[:refresh_token]
       ENV[ACCOUNT_TYPE_VAR] = cred_json[:type]
-      expect(Google::Auth.get_application_default @scope, options)
+      expect(Google::Auth.get_application_default(@scope, options))
         .to_not be_nil
     end
 
@@ -164,7 +174,7 @@ describe '#get_application_default' do
       ENV[REFRESH_TOKEN_VAR] = cred_json[:refresh_token]
       ENV[ACCOUNT_TYPE_VAR] = cred_json[:type]
       expect { Google::Auth.get_application_default @scope, options }.to output(
-          Google::Auth::CredentialsLoader::CLOUD_SDK_CREDENTIALS_WARNING + "\n"
+        Google::Auth::CredentialsLoader::CLOUD_SDK_CREDENTIALS_WARNING + "\n"
       ).to_stderr
     end
   end
@@ -238,9 +248,11 @@ describe '#get_application_default' do
       ENV.delete(@var_name) unless ENV[@var_name].nil?
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, '.config', WELL_KNOWN_PATH)
+        key_path = File.join(dir, WELL_KNOWN_PATH) if OS.windows?
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV['HOME'] = dir
+        ENV['APPDATA'] = dir
         expect do
           Google::Auth.get_application_default @scope, options
         end.to raise_error RuntimeError
diff --git a/spec/googleauth/service_account_spec.rb b/spec/googleauth/service_account_spec.rb
index 799b051..ef86aa0 100644
--- a/spec/googleauth/service_account_spec.rb
+++ b/spec/googleauth/service_account_spec.rb
@@ -40,6 +40,7 @@ require 'multi_json'
 require 'openssl'
 require 'spec_helper'
 require 'tmpdir'
+require 'os'
 
 include Google::Auth::CredentialsLoader
 
@@ -223,6 +224,7 @@ describe Google::Auth::ServiceAccountCredentials do
   describe '#from_well_known_path' do
     before(:example) do
       @home = ENV['HOME']
+      @app_data = ENV['APPDATA']
       @scope = 'https://www.googleapis.com/auth/userinfo.profile'
       @known_path = WELL_KNOWN_PATH
       @clz = ServiceAccountCredentials
@@ -230,6 +232,7 @@ describe Google::Auth::ServiceAccountCredentials do
 
     after(:example) do
       ENV['HOME'] = @home unless @home == ENV['HOME']
+      ENV['APPDATA'] = @app_data unless @app_data == ENV['APPDATA']
     end
 
     it 'is nil if no file exists' do
@@ -240,9 +243,11 @@ describe Google::Auth::ServiceAccountCredentials do
     it 'successfully loads the file when it is present' do
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, '.config', @known_path)
+        key_path = File.join(dir, WELL_KNOWN_PATH) if OS.windows?
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV['HOME'] = dir
+        ENV['APPDATA'] = dir
         expect(@clz.from_well_known_path(@scope)).to_not be_nil
       end
     end
@@ -251,10 +256,16 @@ describe Google::Auth::ServiceAccountCredentials do
   describe '#from_system_default_path' do
     before(:example) do
       @scope = 'https://www.googleapis.com/auth/userinfo.profile'
-      @path = File.join('/etc/google/auth/', CREDENTIALS_FILE_NAME)
+      @program_data = ENV['ProgramData']
+      @prefix = OS.windows? ? '/etc/Google/Auth/' : '/etc/google/auth/'
+      @path = File.join(@prefix, CREDENTIALS_FILE_NAME)
       @clz = ServiceAccountCredentials
     end
 
+    after(:example) do
+      ENV['ProgramData'] = @program_data
+    end
+
     it 'is nil if no file exists' do
       FakeFS do
         expect(ServiceAccountCredentials.from_system_default_path(@scope))
@@ -264,6 +275,7 @@ describe Google::Auth::ServiceAccountCredentials do
 
     it 'successfully loads the file when it is present' do
       FakeFS do
+        ENV['ProgramData'] = '/etc'
         FileUtils.mkdir_p(File.dirname(@path))
         File.write(@path, cred_json_text)
         expect(@clz.from_system_default_path(@scope)).to_not be_nil
@@ -351,10 +363,12 @@ describe Google::Auth::ServiceAccountJwtHeaderCredentials do
   describe '#from_well_known_path' do
     before(:example) do
       @home = ENV['HOME']
+      @app_data = ENV['APPDATA']
     end
 
     after(:example) do
       ENV['HOME'] = @home unless @home == ENV['HOME']
+      ENV['APPDATA'] = @app_data unless @app_data == ENV['APPDATA']
     end
 
     it 'is nil if no file exists' do
@@ -365,9 +379,11 @@ describe Google::Auth::ServiceAccountJwtHeaderCredentials do
     it 'successfully loads the file when it is present' do
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, '.config', WELL_KNOWN_PATH)
+        key_path = File.join(dir, WELL_KNOWN_PATH) if OS.windows?
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV['HOME'] = dir
+        ENV['APPDATA'] = dir
         expect(clz.from_well_known_path).to_not be_nil
       end
     end
diff --git a/spec/googleauth/user_refresh_spec.rb b/spec/googleauth/user_refresh_spec.rb
index 9c7cffd..17068cf 100644
--- a/spec/googleauth/user_refresh_spec.rb
+++ b/spec/googleauth/user_refresh_spec.rb
@@ -40,6 +40,7 @@ require 'multi_json'
 require 'openssl'
 require 'spec_helper'
 require 'tmpdir'
+require 'os'
 
 include Google::Auth::CredentialsLoader
 
@@ -154,6 +155,7 @@ describe Google::Auth::UserRefreshCredentials do
   describe '#from_well_known_path' do
     before(:example) do
       @home = ENV['HOME']
+      @app_data = ENV['APPDATA']
       @scope = 'https://www.googleapis.com/auth/userinfo.profile'
       @known_path = WELL_KNOWN_PATH
       @clz = UserRefreshCredentials
@@ -161,6 +163,7 @@ describe Google::Auth::UserRefreshCredentials do
 
     after(:example) do
       ENV['HOME'] = @home unless @home == ENV['HOME']
+      ENV['APPDATA'] = @app_data unless @app_data == ENV['APPDATA']
     end
 
     it 'is nil if no file exists' do
@@ -173,9 +176,11 @@ describe Google::Auth::UserRefreshCredentials do
       needed.each do |missing|
         Dir.mktmpdir do |dir|
           key_path = File.join(dir, '.config', @known_path)
+          key_path = File.join(dir, @known_path) if OS.windows?
           FileUtils.mkdir_p(File.dirname(key_path))
           File.write(key_path, cred_json_text(missing))
           ENV['HOME'] = dir
+          ENV['APPDATA'] = dir
           expect { @clz.from_well_known_path(@scope) }
             .to raise_error RuntimeError
         end
@@ -185,9 +190,11 @@ describe Google::Auth::UserRefreshCredentials do
     it 'successfully loads the file when it is present' do
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, '.config', @known_path)
+        key_path = File.join(dir, @known_path) if OS.windows?
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV['HOME'] = dir
+        ENV['APPDATA'] = dir
         expect(@clz.from_well_known_path(@scope)).to_not be_nil
       end
     end
@@ -196,10 +203,16 @@ describe Google::Auth::UserRefreshCredentials do
   describe '#from_system_default_path' do
     before(:example) do
       @scope = 'https://www.googleapis.com/auth/userinfo.profile'
-      @path = File.join('/etc/google/auth/', CREDENTIALS_FILE_NAME)
+      @prefix = OS.windows? ? '/etc/Google/Auth/' : '/etc/google/auth/'
+      @path = File.join(@prefix, CREDENTIALS_FILE_NAME)
+      @program_data = ENV['ProgramData']
       @clz = UserRefreshCredentials
     end
 
+    after(:example) do
+      ENV['ProgramData'] = @program_data
+    end
+
     it 'is nil if no file exists' do
       FakeFS do
         expect(UserRefreshCredentials.from_system_default_path(@scope))
@@ -211,6 +224,7 @@ describe Google::Auth::UserRefreshCredentials do
       needed = %w(client_id client_secret refresh_token)
       needed.each do |missing|
         FakeFS do
+          ENV['ProgramData'] = '/etc'
           FileUtils.mkdir_p(File.dirname(@path))
           File.write(@path, cred_json_text(missing))
           expect { @clz.from_system_default_path(@scope) }
@@ -222,6 +236,7 @@ describe Google::Auth::UserRefreshCredentials do
 
     it 'successfully loads the file when it is present' do
       FakeFS do
+        ENV['ProgramData'] = '/etc'
         FileUtils.mkdir_p(File.dirname(@path))
         File.write(@path, cred_json_text)
         expect(@clz.from_system_default_path(@scope)).to_not be_nil