diff --git a/py/makeversionhdr.py b/py/makeversionhdr.py
index d1b41e63b0..5766330989 100644
--- a/py/makeversionhdr.py
+++ b/py/makeversionhdr.py
@@ -6,13 +6,14 @@ This script works with Python 2.6, 2.7, 3.3 and 3.4.
 
 from __future__ import print_function
 
+import argparse
 import sys
 import os
 import datetime
 import subprocess
 
 
-def get_version_info_from_git():
+def get_version_info_from_git(repo_path):
     # Python 2.6 doesn't have check_output, so check for that
     try:
         subprocess.check_output
@@ -24,6 +25,7 @@ def get_version_info_from_git():
     try:
         git_tag = subprocess.check_output(
             ["git", "describe", "--tags", "--dirty", "--always", "--match", "v[1-9].*"],
+            cwd=repo_path,
             stderr=subprocess.STDOUT,
             universal_newlines=True,
         ).strip()
@@ -37,6 +39,7 @@ def get_version_info_from_git():
     try:
         git_hash = subprocess.check_output(
             ["git", "rev-parse", "--short", "HEAD"],
+            cwd=repo_path,
             stderr=subprocess.STDOUT,
             universal_newlines=True,
         ).strip()
@@ -48,11 +51,15 @@ def get_version_info_from_git():
     try:
         # Check if there are any modified files.
         subprocess.check_call(
-            ["git", "diff", "--no-ext-diff", "--quiet", "--exit-code"], stderr=subprocess.STDOUT
+            ["git", "diff", "--no-ext-diff", "--quiet", "--exit-code"],
+            cwd=repo_path,
+            stderr=subprocess.STDOUT,
         )
         # Check if there are any staged files.
         subprocess.check_call(
-            ["git", "diff-index", "--cached", "--quiet", "HEAD", "--"], stderr=subprocess.STDOUT
+            ["git", "diff-index", "--cached", "--quiet", "HEAD", "--"],
+            cwd=repo_path,
+            stderr=subprocess.STDOUT,
         )
     except subprocess.CalledProcessError:
         git_hash += "-dirty"
@@ -62,8 +69,8 @@ def get_version_info_from_git():
     return git_tag, git_hash
 
 
-def get_version_info_from_mpconfig():
-    with open(os.path.join(os.path.dirname(sys.argv[0]), "..", "py", "mpconfig.h")) as f:
+def get_version_info_from_mpconfig(repo_path):
+    with open(os.path.join(repo_path, "py", "mpconfig.h")) as f:
         for line in f:
             if line.startswith("#define MICROPY_VERSION_MAJOR "):
                 ver_major = int(line.strip().split()[2])
@@ -78,11 +85,11 @@ def get_version_info_from_mpconfig():
     return None
 
 
-def make_version_header(filename):
+def make_version_header(repo_path, filename):
     # Get version info using git, with fallback to py/mpconfig.h
-    info = get_version_info_from_git()
+    info = get_version_info_from_git(repo_path)
     if info is None:
-        info = get_version_info_from_mpconfig()
+        info = get_version_info_from_mpconfig(repo_path)
 
     git_tag, git_hash = info
 
@@ -119,5 +126,21 @@ def make_version_header(filename):
             f.write(file_data)
 
 
+def main():
+    parser = argparse.ArgumentParser()
+    # makeversionheader.py lives in repo/py, so default repo_path to the
+    # parent of sys.argv[0]'s directory.
+    parser.add_argument(
+        "-r",
+        "--repo-path",
+        default=os.path.join(os.path.dirname(sys.argv[0]), ".."),
+        help="path to MicroPython Git repo to query for version",
+    )
+    parser.add_argument("dest", nargs=1, help="output file path")
+    args = parser.parse_args()
+
+    make_version_header(args.repo_path, args.dest[0])
+
+
 if __name__ == "__main__":
-    make_version_header(sys.argv[1])
+    main()