diff --git a/index.js b/index.js
index 6f5c076..86e45d3 100644
--- a/index.js
+++ b/index.js
@@ -280,7 +280,7 @@ function runCmd_ (cmd, pkg, env, wd, opts, stage, unsafe, uid, gid, cb_) {
 
   if (customShell) {
     sh = customShell
-  } else if (process.platform === 'win32') {
+  } else if (opts.isWindowsShell == null ? process.platform === 'win32' : opts.isWindowsShell) {
     sh = process.env.comspec || 'cmd'
     shFlag = '/d /s /c'
     conf.windowsVerbatimArguments = true
diff --git a/lib/spawn.js b/lib/spawn.js
index 30e5b81..b6ea61e 100644
--- a/lib/spawn.js
+++ b/lib/spawn.js
@@ -2,8 +2,10 @@
 
 module.exports = spawn
 
+const path = require('path')
 const _spawn = require('child_process').spawn
 const EventEmitter = require('events').EventEmitter
+const _spawnSync = require('child_process').spawnSync
 
 let progressEnabled
 let running = 0
@@ -29,7 +31,49 @@ function willCmdOutput (stdio) {
   return false
 }
 
+function getGitDirByRegstry (arch) {
+  const args = [
+    'QUERY',
+    'HKLM\\SOFTWARE\\GitForWindows',
+    '/v',
+    'InstallPath',
+  ]
+
+  if (arch) {
+    args.push('/reg:' + arch)
+  }
+
+  const stdout = _spawnSync('reg.exe', args).stdout
+
+  if (stdout && /^\s*InstallPath\s+REG(?:_[A-Z]+)+\s+(.+?)$/im.test(stdout.toString())) {
+    return RegExp.$1
+  } else if (arch === 64) {
+    return getGitDirByRegstry(32)
+  }
+}
+
+function getGitPath(cmd) {
+  let gitInstRoot
+  if ('GIT_INSTALL_ROOT' in process.env) {
+    gitInstRoot = process.env.GIT_INSTALL_ROOT
+  } else {
+    const osArch = /64$/.test(process.env.PROCESSOR_ARCHITEW6432 || process.arch) ? 64 : 32
+    gitInstRoot = getGitDirByRegstry(osArch)
+    process.env.GIT_INSTALL_ROOT = gitInstRoot
+  }
+
+  if (gitInstRoot) {
+    cmd = path.join(gitInstRoot, cmd)
+  }
+  return cmd
+}
+
 function spawn (cmd, args, options, log) {
+
+  if (process.platform === "win32" && cmd[0] === "/") {
+    cmd = getGitPath(cmd)
+  }
+
   const cmdWillOutput = willCmdOutput(options && options.stdio)
 
   if (cmdWillOutput) startRunning(log)