diff --git a/py/makeversionhdr.py b/py/makeversionhdr.py
index 2030bb02c4..cb7325e416 100644
--- a/py/makeversionhdr.py
+++ b/py/makeversionhdr.py
@@ -25,7 +25,6 @@ def get_version_info_from_git(repo_path):
     # Python 2.6 doesn't have check_output, so check for that
     try:
         subprocess.check_output
-        subprocess.check_call
     except AttributeError:
         return None
 
@@ -44,9 +43,25 @@ def get_version_info_from_git(repo_path):
             return git_tag[0]
         else:
             return git_tag[0] + "-" + git_tag[1].replace("-", ".")
-    except subprocess.CalledProcessError:
+    except (subprocess.CalledProcessError, OSError):
         return None
-    except OSError:
+
+
+def get_hash_from_git(repo_path):
+    # Python 2.6 doesn't have check_output, so check for that.
+    try:
+        subprocess.check_output
+    except AttributeError:
+        return None
+
+    try:
+        return subprocess.check_output(
+            ["git", "rev-parse", "--short", "HEAD"],
+            cwd=repo_path,
+            stderr=subprocess.STDOUT,
+            universal_newlines=True,
+        ).strip()
+    except (subprocess.CalledProcessError, OSError):
         return None
 
 
@@ -86,10 +101,13 @@ def get_version_info_from_mpconfig(repo_path):
 
 def make_version_header(repo_path, filename):
     git_tag = None
+    git_hash = None
     if "MICROPY_GIT_TAG" in os.environ:
         git_tag = os.environ["MICROPY_GIT_TAG"]
+        git_hash = os.environ.get("MICROPY_GIT_HASH")
     if git_tag is None:
         git_tag = get_version_info_from_git(repo_path)
+        git_hash = get_hash_from_git(repo_path)
     if git_tag is None:
         git_tag = get_version_info_from_mpconfig(repo_path)
 
@@ -104,12 +122,15 @@ def make_version_header(repo_path, filename):
         ).date()
 
     # Generate the file with the git and version info
+    # Note: MICROPY_GIT_HASH may be used by third-party code.
     file_data = """\
 // This file was generated by py/makeversionhdr.py
 #define MICROPY_GIT_TAG "%s"
+#define MICROPY_GIT_HASH "%s"
 #define MICROPY_BUILD_DATE "%s"
 """ % (
         git_tag,
+        git_hash or "<no hash>",
         build_date.strftime("%Y-%m-%d"),
     )