diff --git a/codearchiver/modules/git.py b/codearchiver/modules/git.py
index 6ce3a35..2035e2a 100644
--- a/codearchiver/modules/git.py
+++ b/codearchiver/modules/git.py
@@ -50,17 +50,17 @@ class Git(codearchiver.core.Module):
 		if self._extraBranches:
 			for branch, commit in self._extraBranches.items():
 				_logger.info(f'Fetching commit {commit} as {branch}')
-				r, _ = codearchiver.subprocess.run_with_log(['git', 'fetch', '--verbose', '--progress', 'origin', commit], cwd = directory, check = False)
+				r, _, _ = codearchiver.subprocess.run_with_log(['git', 'fetch', '--verbose', '--progress', 'origin', commit], cwd = directory, check = False)
 				if r == 0:
-					r2, _ = codearchiver.subprocess.run_with_log(['git', 'update-ref', f'refs/codearchiver/{branch}', commit, ''], cwd = directory, check = False)
+					r2, _, _ = codearchiver.subprocess.run_with_log(['git', 'update-ref', f'refs/codearchiver/{branch}', commit, ''], cwd = directory, check = False)
 					if r2 != 0:
 						_logger.error(f'Failed to update-ref refs/codearchiver/{branch} to {commit}')
 				else:
 					_logger.error(f'Failed to fetch {commit}')
 
 		_logger.info(f'Collecting repository metadata for index')
-		_, refs = codearchiver.subprocess.run_with_log(['git', 'show-ref'], cwd = directory)
-		_, commits = codearchiver.subprocess.run_with_log(['git', 'log', '--reflog', '--all', '--format=format:%H% P'], cwd = directory)
+		_, refs, _ = codearchiver.subprocess.run_with_log(['git', 'show-ref'], cwd = directory)
+		_, commits, _ = codearchiver.subprocess.run_with_log(['git', 'log', '--reflog', '--all', '--format=format:%H% P'], cwd = directory)
 		commits = list(map(functools.partial(str.split, sep = ' '), commits.splitlines()))
 		rootCommits = [c[0] for c in commits if len(c) == 1]
 
diff --git a/codearchiver/subprocess.py b/codearchiver/subprocess.py
index 453f7fc..5422851 100644
--- a/codearchiver/subprocess.py
+++ b/codearchiver/subprocess.py
@@ -14,7 +14,7 @@ def run_with_log(args, *, check = True, input = None, **kwargs):
 	`check` has the same semantics as on `subprocess.run`, i.e. raises an exception if the process exits non-zero.
 	`input`, if specified, is a `bytes` object that is fed to the subprocess via stdin.
 	`stdin`, `stdout`, and `stderr` kwargs must not be used.
-	Returns a tuple with the process's exit status and its stdout output.
+	Returns a tuple with the process's exit status, its stdout output, and its stderr output.
 	'''
 	badKwargs = {'stdin', 'stdout', 'stderr'}.intersection(set(kwargs))
 	if badKwargs:
@@ -29,6 +29,7 @@ def run_with_log(args, *, check = True, input = None, **kwargs):
 	sel.register(p.stdout, selectors.EVENT_READ)
 	sel.register(p.stderr, selectors.EVENT_READ)
 	stdout = []
+	stderr = []
 	stderrBuf = b''
 	if input is not None:
 		stdinView = memoryview(input)
@@ -53,6 +54,7 @@ def run_with_log(args, *, check = True, input = None, **kwargs):
 					key.fileobj.close()
 					continue
 				if key.fileobj is p.stderr:
+					stderr.append(data)
 					stderrBuf += data
 					*lines, stderrBuf = stderrBuf.replace(b'\r', b'\n').rsplit(b'\n', 1)
 					if not lines:
@@ -70,4 +72,4 @@ def run_with_log(args, *, check = True, input = None, **kwargs):
 	_logger.info(f'Process exited with status {p.returncode}')
 	if check and p.returncode != 0:
 		raise subprocess.CalledProcessError(returncode = p.returncode, cmd = args)
-	return (p.returncode, b''.join(stdout).decode('utf-8'))
+	return (p.returncode, b''.join(stdout).decode('utf-8'), b''.join(stderr).decode('utf-8'))