diff --git a/tempfile.c b/tempfile.c
index 0b5d8ce92..0af7ebf01 100644
--- a/tempfile.c
+++ b/tempfile.c
@@ -137,6 +137,14 @@ int create_tempfile(struct tempfile *tempfile, const char *path)
 	return tempfile->fd;
 }
 
+void register_tempfile(struct tempfile *tempfile, const char *path)
+{
+	prepare_tempfile_object(tempfile);
+	strbuf_add_absolute_path(&tempfile->filename, path);
+	tempfile->owner = getpid();
+	tempfile->active = 1;
+}
+
 int mks_tempfile_sm(struct tempfile *tempfile,
 		    const char *template, int suffixlen, int mode)
 {
diff --git a/tempfile.h b/tempfile.h
index a30e12c7e..4219fe41b 100644
--- a/tempfile.h
+++ b/tempfile.h
@@ -92,6 +92,14 @@ struct tempfile {
  */
 extern int create_tempfile(struct tempfile *tempfile, const char *path);
 
+/*
+ * Register an existing file as a tempfile, meaning that it will be
+ * deleted when the program exits. The tempfile is considered closed,
+ * but it can be worked with like any other closed tempfile (for
+ * example, it can be opened using reopen_tempfile()).
+ */
+extern void register_tempfile(struct tempfile *tempfile, const char *path);
+
 
 /*
  * mks_tempfile functions