diff --git a/src/idxmap.h b/src/idxmap.h
index 74304bb97..4122a89fe 100644
--- a/src/idxmap.h
+++ b/src/idxmap.h
@@ -70,6 +70,7 @@ static kh_inline khint_t idxentry_hash(const git_index_entry *e)
 #define git_idxmap_valid_index(h, idx) (idx != kh_end(h))
 #define git_idxmap_has_data(h, idx) kh_exist(h, idx)
 
+#define git_idxmap_resize(h,s)  kh_resize(idx, h, s)
 #define git_idxmap_free(h)  kh_destroy(idx, h), h = NULL
 #define git_idxmap_clear(h) kh_clear(idx, h)
 
diff --git a/src/index.c b/src/index.c
index 60e4d443c..5c7bd90dd 100644
--- a/src/index.c
+++ b/src/index.c
@@ -879,6 +879,18 @@ void git_index_entry__init_from_stat(
 	entry->file_size = st->st_size;
 }
 
+static void index_entry_adjust_namemask(
+		git_index_entry *entry,
+		size_t path_length)
+{
+	entry->flags &= ~GIT_IDXENTRY_NAMEMASK;
+
+	if (path_length < GIT_IDXENTRY_NAMEMASK)
+		entry->flags |= path_length & GIT_IDXENTRY_NAMEMASK;
+	else
+		entry->flags |= GIT_IDXENTRY_NAMEMASK;
+}
+
 static int index_entry_create(
 	git_index_entry **out,
 	git_repository *repo,
@@ -1279,13 +1291,7 @@ static int index_insert(
 
 	/* make sure that the path length flag is correct */
 	path_length = ((struct entry_internal *)entry)->pathlen;
-
-	entry->flags &= ~GIT_IDXENTRY_NAMEMASK;
-
-	if (path_length < GIT_IDXENTRY_NAMEMASK)
-		entry->flags |= path_length & GIT_IDXENTRY_NAMEMASK;
-	else
-		entry->flags |= GIT_IDXENTRY_NAMEMASK;
+	index_entry_adjust_namemask(entry, path_length);
 
 	/* this entry is now up-to-date and should not be checked for raciness */
 	entry->flags_extended |= GIT_IDXENTRY_UPTODATE;
@@ -1550,21 +1556,28 @@ int git_index__fill(git_index *index, const git_vector *source_entries)
 
 	assert(index);
 
+	if (!source_entries->length)
+		return 0;
+
 	if (git_mutex_lock(&index->lock) < 0) {
 		giterr_set(GITERR_OS, "Unable to acquire index lock");
 		return -1;
 	}
 
+	git_vector_size_hint(&index->entries, source_entries->length);
+	git_idxmap_resize(index->entries_map, source_entries->length * 1.3);
+
 	git_vector_foreach(source_entries, i, source_entry) {
 		git_index_entry *entry = NULL;
 
 		if ((ret = index_entry_dup(&entry, index, source_entry)) < 0)
 			break;
 
+		index_entry_adjust_namemask(entry, ((struct entry_internal *)entry)->pathlen);
 		entry->flags_extended |= GIT_IDXENTRY_UPTODATE;
+		entry->mode = git_index__create_mode(entry->mode);
 
-		ret = git_vector_insert(&index->entries, entry);
-		if (ret < 0)
+		if ((ret = git_vector_insert(&index->entries, entry)) < 0)
 			break;
 
 		INSERT_IN_MAP(index, entry, ret);
@@ -2889,11 +2902,7 @@ static int read_tree_cb(
 		entry->flags_extended = 0;
 	}
 
-	if (path.size < GIT_IDXENTRY_NAMEMASK)
-		entry->flags = path.size & GIT_IDXENTRY_NAMEMASK;
-	else
-		entry->flags = GIT_IDXENTRY_NAMEMASK;
-
+	index_entry_adjust_namemask(entry, path.size);
 	git_buf_free(&path);
 
 	if (git_vector_insert(data->new_entries, entry) < 0) {
diff --git a/src/vector.c b/src/vector.c
index 93d09bb5b..a81d463ef 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -40,6 +40,13 @@ GIT_INLINE(int) resize_vector(git_vector *v, size_t new_size)
 	return 0;
 }
 
+int git_vector_size_hint(git_vector *v, size_t size_hint)
+{
+	if (v->_alloc_size >= size_hint)
+		return 0;
+	return resize_vector(v, size_hint);
+}
+
 int git_vector_dup(git_vector *v, const git_vector *src, git_vector_cmp cmp)
 {
 	size_t bytes;
diff --git a/src/vector.h b/src/vector.h
index aac46c4b3..b7500ded3 100644
--- a/src/vector.h
+++ b/src/vector.h
@@ -32,6 +32,7 @@ void git_vector_free_deep(git_vector *v); /* free each entry and self */
 void git_vector_clear(git_vector *v);
 int git_vector_dup(git_vector *v, const git_vector *src, git_vector_cmp cmp);
 void git_vector_swap(git_vector *a, git_vector *b);
+int git_vector_size_hint(git_vector *v, size_t size_hint);
 
 void **git_vector_detach(size_t *size, size_t *asize, git_vector *v);