diff --git a/run-command.c b/run-command.c
index e3e02475cc..89dbe62ab8 100644
--- a/run-command.c
+++ b/run-command.c
@@ -1847,7 +1847,7 @@ int run_auto_maintenance(int quiet)
 	return run_command(&maint);
 }
 
-void prepare_other_repo_env(struct strvec *env, const char *new_git_dir)
+void sanitize_repo_env(struct strvec *env)
 {
 	const char * const *var;
 
@@ -1856,6 +1856,11 @@ void prepare_other_repo_env(struct strvec *env, const char *new_git_dir)
 		    strcmp(*var, CONFIG_COUNT_ENVIRONMENT))
 			strvec_push(env, *var);
 	}
+}
+
+void prepare_other_repo_env(struct strvec *env, const char *new_git_dir)
+{
+	sanitize_repo_env(env);
 	strvec_pushf(env, "%s=%s", GIT_DIR_ENVIRONMENT, new_git_dir);
 }
 
diff --git a/run-command.h b/run-command.h
index 0df25e445f..7e5a263ee6 100644
--- a/run-command.h
+++ b/run-command.h
@@ -509,13 +509,18 @@ struct run_process_parallel_opts
  */
 void run_processes_parallel(const struct run_process_parallel_opts *opts);
 
+/**
+ * Unset all local-repo GIT_* variables in env; see local_repo_env in
+ * environment.h. GIT_CONFIG_PARAMETERS and GIT_CONFIG_COUNT are preserved
+ * to pass -c and --config-env options from the parent process.
+ */
+void sanitize_repo_env(struct strvec *env);
+
 /**
  * Convenience function which prepares env for a command to be run in a
- * new repo. This adds all GIT_* environment variables to env with the
- * exception of GIT_CONFIG_PARAMETERS and GIT_CONFIG_COUNT (which cause the
- * corresponding environment variables to be unset in the subprocess) and adds
- * an environment variable pointing to new_git_dir. See local_repo_env in
- * environment.h for more information.
+ * new repo. This removes variables pointing to the local repository (using
+ * sanitize_repo_env() above), and adds an environment variable pointing to
+ * new_git_dir.
  */
 void prepare_other_repo_env(struct strvec *env, const char *new_git_dir);