diff --git a/builtin/repack.c b/builtin/repack.c
index 82c19b7555..45583683ee 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -431,8 +431,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 			char *fname, *fname_old;
 
 			if (!midx_cleared) {
-				/* if we move a packfile, it will invalidated the midx */
-				clear_midx_file(get_object_directory());
+				clear_midx_file(the_repository);
 				midx_cleared = 1;
 			}
 
@@ -561,6 +560,10 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	if (!no_update_server_info)
 		update_server_info(0);
 	remove_temporary_files();
+
+	if (git_env_bool(GIT_TEST_MULTI_PACK_INDEX, 0))
+		write_midx_file(get_object_directory());
+
 	string_list_clear(&names, 0);
 	string_list_clear(&rollback, 0);
 	string_list_clear(&existing_packs, 0);
diff --git a/midx.c b/midx.c
index 4fac0cd08a..a50b117b77 100644
--- a/midx.c
+++ b/midx.c
@@ -176,9 +176,13 @@ cleanup_fail:
 	return NULL;
 }
 
-static void close_midx(struct multi_pack_index *m)
+void close_midx(struct multi_pack_index *m)
 {
 	uint32_t i;
+
+	if (!m)
+		return;
+
 	munmap((unsigned char *)m->data, m->data_len);
 	close(m->fd);
 	m->fd = -1;
@@ -186,7 +190,7 @@ static void close_midx(struct multi_pack_index *m)
 	for (i = 0; i < m->num_packs; i++) {
 		if (m->packs[i]) {
 			close_pack(m->packs[i]);
-			free(m->packs);
+			free(m->packs[i]);
 		}
 	}
 	FREE_AND_NULL(m->packs);
@@ -331,9 +335,14 @@ int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, i
 	struct multi_pack_index *m;
 	struct multi_pack_index *m_search;
 	int config_value;
+	static int env_value = -1;
 
-	if (repo_config_get_bool(r, "core.multipackindex", &config_value) ||
-	    !config_value)
+	if (env_value < 0)
+		env_value = git_env_bool(GIT_TEST_MULTI_PACK_INDEX, 0);
+
+	if (!env_value &&
+	    (repo_config_get_bool(r, "core.multipackindex", &config_value) ||
+	    !config_value))
 		return 0;
 
 	for (m_search = r->objects->multi_pack_index; m_search; m_search = m_search->next)
@@ -914,9 +923,14 @@ cleanup:
 	return 0;
 }
 
-void clear_midx_file(const char *object_dir)
+void clear_midx_file(struct repository *r)
 {
-	char *midx = get_midx_filename(object_dir);
+	char *midx = get_midx_filename(r->objects->objectdir);
+
+	if (r->objects && r->objects->multi_pack_index) {
+		close_midx(r->objects->multi_pack_index);
+		r->objects->multi_pack_index = NULL;
+	}
 
 	if (remove_path(midx)) {
 		UNLEAK(midx);
diff --git a/midx.h b/midx.h
index 1d6c21afe3..774f652530 100644
--- a/midx.h
+++ b/midx.h
@@ -6,6 +6,8 @@
 struct object_id;
 struct pack_entry;
 
+#define GIT_TEST_MULTI_PACK_INDEX "GIT_TEST_MULTI_PACK_INDEX"
+
 struct multi_pack_index {
 	struct multi_pack_index *next;
 
@@ -45,7 +47,9 @@ int midx_contains_pack(struct multi_pack_index *m, const char *idx_name);
 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local);
 
 int write_midx_file(const char *object_dir);
-void clear_midx_file(const char *object_dir);
+void clear_midx_file(struct repository *r);
 int verify_midx_file(const char *object_dir);
 
+void close_midx(struct multi_pack_index *m);
+
 #endif
diff --git a/packfile.c b/packfile.c
index f2850a00b5..d1e6683ffe 100644
--- a/packfile.c
+++ b/packfile.c
@@ -345,6 +345,11 @@ void close_all_packs(struct raw_object_store *o)
 			BUG("want to close pack marked 'do-not-close'");
 		else
 			close_pack(p);
+
+	if (o->multi_pack_index) {
+		close_midx(o->multi_pack_index);
+		o->multi_pack_index = NULL;
+	}
 }
 
 /*
diff --git a/t/README b/t/README
index 2e9bef2852..242497455f 100644
--- a/t/README
+++ b/t/README
@@ -344,6 +344,10 @@ of the index for the whole test suite by bypassing the default number of
 cache entries and thread minimums. Setting this to 1 will make the
 index loading single threaded.
 
+GIT_TEST_MULTI_PACK_INDEX=<boolean>, when true, forces the multi-pack-
+index to be written after every 'git repack' command, and overrides the
+'core.multiPackIndex' setting to true.
+
 Naming Tests
 ------------
 
diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index 1be3459c5b..82d7f7f6a5 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -191,6 +191,7 @@ test_expect_success 'pack-objects respects --honor-pack-keep (local bitmapped pa
 
 test_expect_success 'pack-objects respects --local (non-local bitmapped pack)' '
 	mv .git/objects/pack/$packbitmap.* alt.git/objects/pack/ &&
+	rm -f .git/objects/pack/multi-pack-index &&
 	test_when_finished "mv alt.git/objects/pack/$packbitmap.* .git/objects/pack/" &&
 	echo HEAD | git pack-objects --local --stdout --revs >3b.pack &&
 	git index-pack 3b.pack &&
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index bd8e841b81..70926b5bc0 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -271,7 +271,7 @@ test_expect_success 'git-fsck incorrect offset' '
 
 test_expect_success 'repack removes multi-pack-index' '
 	test_path_is_file $objdir/pack/multi-pack-index &&
-	git repack -adf &&
+	GIT_TEST_MULTI_PACK_INDEX=0 git repack -adf &&
 	test_path_is_missing $objdir/pack/multi-pack-index
 '
 
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index 40fe7e4976..59a13b6a77 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -1558,7 +1558,7 @@ test_expect_success 'O: blank lines not necessary after other commands' '
 	INPUT_END
 
 	git fast-import <input &&
-	test 8 = $(find .git/objects/pack -type f | wc -l) &&
+	test 8 = $(find .git/objects/pack -type f | grep -v multi-pack-index | wc -l) &&
 	test $(git rev-parse refs/tags/O3-2nd) = $(git rev-parse O3^) &&
 	git log --reverse --pretty=oneline O3 | sed s/^.*z// >actual &&
 	test_cmp expect actual