diff --git a/builtin/repack.c b/builtin/repack.c
index 279be11a16..2158b48f4c 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -14,6 +14,7 @@
 #include "object-store.h"
 #include "promisor-remote.h"
 #include "shallow.h"
+#include "pack.h"
 
 static int delta_base_offset = 1;
 static int pack_kept_objects = -1;
@@ -263,7 +264,7 @@ static void repack_promisor_objects(const struct pack_objects_args *args,
 	while (strbuf_getline_lf(&line, out) != EOF) {
 		struct string_list_item *item;
 		char *promisor_name;
-		int fd;
+
 		if (line.len != the_hash_algo->hexsz)
 			die(_("repack: Expecting full hex object ID lines only from pack-objects."));
 		item = string_list_append(names, line.buf);
@@ -281,10 +282,7 @@ static void repack_promisor_objects(const struct pack_objects_args *args,
 		 */
 		promisor_name = mkpathdup("%s-%s.promisor", packtmp,
 					  line.buf);
-		fd = open(promisor_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
-		if (fd < 0)
-			die_errno(_("unable to create '%s'"), promisor_name);
-		close(fd);
+		write_promisor_file(promisor_name, NULL, 0);
 
 		item->util = (void *)(uintptr_t)populate_pack_exts(item->string);
 
diff --git a/fetch-pack.c b/fetch-pack.c
index 876f90c759..1eaedcb5dc 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -772,13 +772,11 @@ static int sideband_demux(int in, int out, void *data)
 	return ret;
 }
 
-static void write_promisor_file(const char *keep_name,
-				struct ref **sought, int nr_sought)
+static void create_promisor_file(const char *keep_name,
+				 struct ref **sought, int nr_sought)
 {
 	struct strbuf promisor_name = STRBUF_INIT;
 	int suffix_stripped;
-	FILE *output;
-	int i;
 
 	strbuf_addstr(&promisor_name, keep_name);
 	suffix_stripped = strbuf_strip_suffix(&promisor_name, ".keep");
@@ -787,11 +785,7 @@ static void write_promisor_file(const char *keep_name,
 		    keep_name);
 	strbuf_addstr(&promisor_name, ".promisor");
 
-	output = xfopen(promisor_name.buf, "w");
-	for (i = 0; i < nr_sought; i++)
-		fprintf(output, "%s %s\n", oid_to_hex(&sought[i]->old_oid),
-			sought[i]->name);
-	fclose(output);
+	write_promisor_file(promisor_name.buf, sought, nr_sought);
 
 	strbuf_release(&promisor_name);
 }
@@ -875,7 +869,7 @@ static int get_pack(struct fetch_pack_args *args,
 
 		if (args->from_promisor)
 			/*
-			 * write_promisor_file() may be called afterwards but
+			 * create_promisor_file() may be called afterwards but
 			 * we still need index-pack to know that this is a
 			 * promisor pack. For example, if transfer.fsckobjects
 			 * is true, index-pack needs to know that .gitmodules
@@ -943,7 +937,7 @@ static int get_pack(struct fetch_pack_args *args,
 	 * obtained .keep filename if necessary
 	 */
 	if (do_keep && pack_lockfiles && pack_lockfiles->nr && args->from_promisor)
-		write_promisor_file(pack_lockfiles->items[0].string, sought, nr_sought);
+		create_promisor_file(pack_lockfiles->items[0].string, sought, nr_sought);
 
 	return 0;
 }
diff --git a/pack-write.c b/pack-write.c
index 3513665e1e..e9bb3fd949 100644
--- a/pack-write.c
+++ b/pack-write.c
@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "pack.h"
 #include "csum-file.h"
+#include "remote.h"
 
 void reset_pack_idx_option(struct pack_idx_option *opts)
 {
@@ -367,3 +368,18 @@ void finish_tmp_packfile(struct strbuf *name_buffer,
 
 	free((void *)idx_tmp_name);
 }
+
+void write_promisor_file(const char *promisor_name, struct ref **sought, int nr_sought)
+{
+	int i, err;
+	FILE *output = xfopen(promisor_name, "w");
+
+	for (i = 0; i < nr_sought; i++)
+		fprintf(output, "%s %s\n", oid_to_hex(&sought[i]->old_oid),
+			sought[i]->name);
+
+	err = ferror(output);
+	err |= fclose(output);
+	if (err)
+		die(_("could not write '%s' promisor file"), promisor_name);
+}
diff --git a/pack.h b/pack.h
index 9fc0945ac9..9ae640f417 100644
--- a/pack.h
+++ b/pack.h
@@ -87,6 +87,10 @@ off_t write_pack_header(struct hashfile *f, uint32_t);
 void fixup_pack_header_footer(int, unsigned char *, const char *, uint32_t, unsigned char *, off_t);
 char *index_pack_lockfile(int fd);
 
+struct ref;
+
+void write_promisor_file(const char *promisor_name, struct ref **sought, int nr_sought);
+
 /*
  * The "hdr" output buffer should be at least this big, which will handle sizes
  * up to 2^67.