diff --git a/Documentation/git-pack-objects.txt b/Documentation/git-pack-objects.txt
index d94edcd4b4..cdab9ed503 100644
--- a/Documentation/git-pack-objects.txt
+++ b/Documentation/git-pack-objects.txt
@@ -51,8 +51,7 @@ base-name::
 	<base-name> to determine the name of the created file.
 	When this option is used, the two files are written in
 	<base-name>-<SHA-1>.{pack,idx} files.  <SHA-1> is a hash
-	of the sorted object names to make the resulting filename
-	based on the pack content, and written to the standard
+	based on the pack content and is written to the standard
 	output of the command.
 
 --stdout::
diff --git a/csum-file.c b/csum-file.c
index 53f5375b6c..465971c7f3 100644
--- a/csum-file.c
+++ b/csum-file.c
@@ -11,7 +11,7 @@
 #include "progress.h"
 #include "csum-file.h"
 
-static void flush(struct sha1file *f, void *buf, unsigned int count)
+static void flush(struct sha1file *f, const void *buf, unsigned int count)
 {
 	if (0 <= f->check_fd && count)  {
 		unsigned char check_buffer[8192];
@@ -86,13 +86,13 @@ int sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
 	return fd;
 }
 
-int sha1write(struct sha1file *f, void *buf, unsigned int count)
+int sha1write(struct sha1file *f, const void *buf, unsigned int count)
 {
 	while (count) {
 		unsigned offset = f->offset;
 		unsigned left = sizeof(f->buffer) - offset;
 		unsigned nr = count > left ? left : count;
-		void *data;
+		const void *data;
 
 		if (f->do_crc)
 			f->crc32 = crc32(f->crc32, buf, nr);
diff --git a/csum-file.h b/csum-file.h
index 3b540bdc21..9dedb038ea 100644
--- a/csum-file.h
+++ b/csum-file.h
@@ -34,7 +34,7 @@ extern struct sha1file *sha1fd(int fd, const char *name);
 extern struct sha1file *sha1fd_check(const char *name);
 extern struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp);
 extern int sha1close(struct sha1file *, unsigned char *, unsigned int);
-extern int sha1write(struct sha1file *, void *, unsigned int);
+extern int sha1write(struct sha1file *, const void *, unsigned int);
 extern void sha1flush(struct sha1file *f);
 extern void crc32_begin(struct sha1file *);
 extern uint32_t crc32_end(struct sha1file *);
diff --git a/pack-write.c b/pack-write.c
index ca9e63be18..ddc174e1ad 100644
--- a/pack-write.c
+++ b/pack-write.c
@@ -44,14 +44,13 @@ static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
  */
 const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
 			   int nr_objects, const struct pack_idx_option *opts,
-			   unsigned char *sha1)
+			   const unsigned char *sha1)
 {
 	struct sha1file *f;
 	struct pack_idx_entry **sorted_by_sha, **list, **last;
 	off_t last_obj_offset = 0;
 	uint32_t array[256];
 	int i, fd;
-	git_SHA_CTX ctx;
 	uint32_t index_version;
 
 	if (nr_objects) {
@@ -114,9 +113,6 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 	}
 	sha1write(f, array, 256 * 4);
 
-	/* compute the SHA1 hash of sorted object names. */
-	git_SHA1_Init(&ctx);
-
 	/*
 	 * Write the actual SHA1 entries..
 	 */
@@ -128,7 +124,6 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 			sha1write(f, &offset, 4);
 		}
 		sha1write(f, obj->sha1, 20);
-		git_SHA1_Update(&ctx, obj->sha1, 20);
 		if ((opts->flags & WRITE_IDX_STRICT) &&
 		    (i && !hashcmp(list[-2]->sha1, obj->sha1)))
 			die("The same object %s appears twice in the pack",
@@ -178,7 +173,6 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 	sha1write(f, sha1, 20);
 	sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
 			    ? CSUM_CLOSE : CSUM_FSYNC));
-	git_SHA1_Final(sha1, &ctx);
 	return index_name;
 }
 
diff --git a/pack.h b/pack.h
index aa6ee7d606..12d951659c 100644
--- a/pack.h
+++ b/pack.h
@@ -76,7 +76,7 @@ struct pack_idx_entry {
 struct progress;
 typedef int (*verify_fn)(const unsigned char*, enum object_type, unsigned long, void*, int*);
 
-extern const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects, int nr_objects, const struct pack_idx_option *, unsigned char *sha1);
+extern const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects, int nr_objects, const struct pack_idx_option *, const unsigned char *sha1);
 extern int check_pack_crc(struct packed_git *p, struct pack_window **w_curs, off_t offset, off_t len, unsigned int nr);
 extern int verify_pack_index(struct packed_git *);
 extern int verify_pack(struct packed_git *, verify_fn fn, struct progress *, uint32_t);
diff --git a/t/t5302-pack-index.sh b/t/t5302-pack-index.sh
index fe82025d4a..4bbb718751 100755
--- a/t/t5302-pack-index.sh
+++ b/t/t5302-pack-index.sh
@@ -174,11 +174,11 @@ test_expect_success \
 test_expect_success \
     '[index v1] 5) pack-objects happily reuses corrupted data' \
     'pack4=$(git pack-objects test-4 <obj-list) &&
-     test -f "test-4-${pack1}.pack"'
+     test -f "test-4-${pack4}.pack"'
 
 test_expect_success \
     '[index v1] 6) newly created pack is BAD !' \
-    'test_must_fail git verify-pack -v "test-4-${pack1}.pack"'
+    'test_must_fail git verify-pack -v "test-4-${pack4}.pack"'
 
 test_expect_success \
     '[index v2] 1) stream pack to repository' \