diff --git a/.travis.yml b/.travis.yml
index 99b8078..326dfe1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,7 @@ language: python
 python: 3.6
 
 install:
-- pip install wheel flake8 requests six py7zr bringbuf
+- pip install wheel flake8 requests six py7zr
 
 script:
 - flake8 aqt bin
diff --git a/aqt/cli.py b/aqt/cli.py
index 734798a..63beaaa 100644
--- a/aqt/cli.py
+++ b/aqt/cli.py
@@ -68,7 +68,12 @@ class Cli():
         mirror = args.base
         sevenzip = args.external
         if sevenzip is not None:
-            if not os.path.exists(sevenzip):
+            if sevenzip == '_auto':
+                if platform.system() == 'Windows':
+                    sevenzip = r'C:\Program Files\7-Zip\7z.exe'
+                else:
+                    sevenzip = r'7zr'
+            elif not os.path.exists(sevenzip):
                 print('Specified unexist external command in option -E')
                 exit(1)
         elif sys.version_info.major == 2:
@@ -135,7 +140,7 @@ class Cli():
         install_parser.add_argument('-b', '--base', nargs='?',
                                     help="Specify mirror base url such as http://mirrors.ocf.berkeley.edu/qt/, "
                                          "where 'online' folder exist.")
-        install_parser.add_argument('-E', '--external', nargs='?',
+        install_parser.add_argument('-E', '--external', nargs='?', const='_auto',
                                     help='Use external 7zip command instead of internal extractor.')
         list_parser = subparsers.add_parser('list')
         list_parser.set_defaults(func=self.run_list)
diff --git a/ci/steps.yml b/ci/steps.yml
index f579472..a54e017 100644
--- a/ci/steps.yml
+++ b/ci/steps.yml
@@ -24,7 +24,7 @@ steps:
     inputs:
       scriptSource: filePath
       scriptPath: $(Build.SourcesDirectory)/bin/aqt
-      arguments: install $(QT_VERSION) $(HOST) $(TARGET) $(ARCH)
+      arguments: install $(QT_VERSION) $(HOST) $(TARGET) $(ARCH) -E
       workingDirectory: $(Build.BinariesDirectory)
     condition: not(variables['QT_BASE_MIRROR'])
     displayName: Run Aqt (No Base URL Set)
@@ -32,7 +32,7 @@ steps:
     inputs:
       scriptSource: filePath
       scriptPath: $(Build.SourcesDirectory)/bin/aqt
-      arguments: install $(QT_VERSION) $(HOST) $(TARGET) $(ARCH) -b $(QT_BASE_MIRROR)
+      arguments: install $(QT_VERSION) $(HOST) $(TARGET) $(ARCH) -b $(QT_BASE_MIRROR) -E
       workingDirectory: $(Build.BinariesDirectory)
     condition: variables['QT_BASE_MIRROR']
     displayName: Run Aqt (Base URL Set)
diff --git a/requirements.txt b/requirements.txt
index 75e41b5..78f38c5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,4 +7,3 @@ flake8
 wheel
 twine
 py7zr
-bringbuf