diff --git a/http.c b/http.c
index d59e59f66b..9642cad2e3 100644
--- a/http.c
+++ b/http.c
@@ -19,6 +19,7 @@
 #include "string-list.h"
 #include "object-file.h"
 #include "object-store-ll.h"
+#include "tempfile.h"
 
 static struct trace_key trace_curl = TRACE_KEY_INIT(CURL);
 static int trace_curl_data = 1;
@@ -2388,8 +2389,24 @@ static char *fetch_pack_index(unsigned char *hash, const char *base_url)
 	strbuf_addf(&buf, "objects/pack/pack-%s.idx", hash_to_hex(hash));
 	url = strbuf_detach(&buf, NULL);
 
-	strbuf_addf(&buf, "%s.temp", sha1_pack_index_name(hash));
-	tmp = strbuf_detach(&buf, NULL);
+	/*
+	 * Don't put this into packs/, since it's just temporary and we don't
+	 * want to confuse it with our local .idx files.  We'll generate our
+	 * own index if we choose to download the matching packfile.
+	 *
+	 * It's tempting to use xmks_tempfile() here, but it's important that
+	 * the file not exist, otherwise http_get_file() complains. So we
+	 * create a filename that should be unique, and then just register it
+	 * as a tempfile so that it will get cleaned up on exit.
+	 *
+	 * In theory we could hold on to the tempfile and delete these as soon
+	 * as we download the matching pack, but it would take a bit of
+	 * refactoring. Leaving them until the process ends is probably OK.
+	 */
+	tmp = xstrfmt("%s/tmp_pack_%s.idx",
+		      repo_get_object_directory(the_repository),
+		      hash_to_hex(hash));
+	register_tempfile(tmp);
 
 	if (http_get_file(url, tmp, NULL) != HTTP_OK) {
 		error("Unable to get pack index %s", url);
@@ -2427,10 +2444,8 @@ static int fetch_and_setup_pack_index(struct packed_git **packs_head,
 	}
 
 	ret = verify_pack_index(new_pack);
-	if (!ret) {
+	if (!ret)
 		close_pack_index(new_pack);
-		ret = finalize_object_file(tmp_idx, sha1_pack_index_name(sha1));
-	}
 	free(tmp_idx);
 	if (ret)
 		return -1;
diff --git a/packfile.c b/packfile.c
index df4ba67719..16d3bcf7f7 100644
--- a/packfile.c
+++ b/packfile.c
@@ -237,13 +237,22 @@ static struct packed_git *alloc_packed_git(int extra)
 	return p;
 }
 
+static char *pack_path_from_idx(const char *idx_path)
+{
+	size_t len;
+	if (!strip_suffix(idx_path, ".idx", &len))
+		BUG("idx path does not end in .idx: %s", idx_path);
+	return xstrfmt("%.*s.pack", (int)len, idx_path);
+}
+
 struct packed_git *parse_pack_index(unsigned char *sha1, const char *idx_path)
 {
-	const char *path = sha1_pack_name(sha1);
+	char *path = pack_path_from_idx(idx_path);
 	size_t alloc = st_add(strlen(path), 1);
 	struct packed_git *p = alloc_packed_git(alloc);
 
 	memcpy(p->pack_name, path, alloc); /* includes NUL */
+	free(path);
 	hashcpy(p->hash, sha1, the_repository->hash_algo);
 	if (check_packed_git_idx(idx_path, p)) {
 		free(p);
diff --git a/t/t5550-http-fetch-dumb.sh b/t/t5550-http-fetch-dumb.sh
index 3968b82260..706540ab74 100755
--- a/t/t5550-http-fetch-dumb.sh
+++ b/t/t5550-http-fetch-dumb.sh
@@ -335,7 +335,7 @@ test_expect_success 'fetch can handle previously-fetched .idx files' '
 	count_fetches 1 pack one.trace &&
 	GIT_TRACE_CURL=$PWD/two.trace git --git-dir=clone_packed_branches.git \
 		fetch "$HTTPD_URL"/dumb/repo_packed_branches.git branch2:branch2 &&
-	count_fetches 0 idx two.trace &&
+	count_fetches 1 idx two.trace &&
 	count_fetches 1 pack two.trace
 '
 
@@ -521,4 +521,14 @@ test_expect_success 'fetching via http alternates works' '
 	git -c http.followredirects=true clone "$HTTPD_URL/dumb/alt-child.git"
 '
 
+test_expect_success 'dumb http can fetch index v1' '
+	server=$HTTPD_DOCUMENT_ROOT_PATH/idx-v1.git &&
+	git init --bare "$server" &&
+	git -C "$server" --work-tree=. commit --allow-empty -m foo &&
+	git -C "$server" -c pack.indexVersion=1 gc &&
+
+	git clone "$HTTPD_URL/dumb/idx-v1.git" &&
+	git -C idx-v1 fsck
+'
+
 test_done