diff --git a/sphinx/__init__.py b/sphinx/__init__.py
index 3aecfbfcc..8caea80d0 100644
--- a/sphinx/__init__.py
+++ b/sphinx/__init__.py
@@ -56,6 +56,7 @@ if __version__.endswith('+'):
     __version__ = __version__[:-1]  # remove '+' for PEP-440 version spec.
     try:
         ret = subprocess.run(['git', 'show', '-s', '--pretty=format:%h'],
+                             cwd=package_dir,
                              stdout=PIPE, stderr=PIPE)
         if ret.stdout:
             __display_version__ += '/' + ret.stdout.decode('ascii').strip()