diff --git a/list-objects-filter-options.c b/list-objects-filter-options.c
index 56a1933a50..d46ce4acc4 100644
--- a/list-objects-filter-options.c
+++ b/list-objects-filter-options.c
@@ -202,10 +202,10 @@ static int allow_unencoded(char ch)
 static void filter_spec_append_urlencode(
 	struct list_objects_filter_options *filter, const char *raw)
 {
-	struct strbuf buf = STRBUF_INIT;
-	strbuf_addstr_urlencode(&buf, raw, allow_unencoded);
-	trace_printf("Add to combine filter-spec: %s\n", buf.buf);
-	string_list_append_nodup(&filter->filter_spec, strbuf_detach(&buf, NULL));
+	size_t orig_len = filter->filter_spec.len;
+	strbuf_addstr_urlencode(&filter->filter_spec, raw, allow_unencoded);
+	trace_printf("Add to combine filter-spec: %s\n",
+		     filter->filter_spec.buf + orig_len);
 }
 
 /*
@@ -229,7 +229,7 @@ static void transform_to_combine_type(
 	}
 	filter_options->sub_nr = 1;
 	filter_options->choice = LOFC_COMBINE;
-	string_list_append(&filter_options->filter_spec, "combine:");
+	strbuf_addstr(&filter_options->filter_spec, "combine:");
 	filter_spec_append_urlencode(
 		filter_options,
 		list_objects_filter_spec(&filter_options->sub[0]));
@@ -237,7 +237,7 @@ static void transform_to_combine_type(
 	 * We don't need the filter_spec strings for subfilter specs, only the
 	 * top level.
 	 */
-	string_list_clear(&filter_options->sub[0].filter_spec, /*free_util=*/0);
+	strbuf_release(&filter_options->sub[0].filter_spec);
 }
 
 void list_objects_filter_die_if_populated(
@@ -254,11 +254,11 @@ void parse_list_objects_filter(
 	struct strbuf errbuf = STRBUF_INIT;
 	int parse_error;
 
-	if (!filter_options->filter_spec.strdup_strings)
+	if (!filter_options->filter_spec.buf)
 		BUG("filter_options not properly initialized");
 
 	if (!filter_options->choice) {
-		string_list_append(&filter_options->filter_spec, arg);
+		strbuf_addstr(&filter_options->filter_spec, arg);
 
 		parse_error = gently_parse_list_objects_filter(
 			filter_options, arg, &errbuf);
@@ -269,7 +269,7 @@ void parse_list_objects_filter(
 		 */
 		transform_to_combine_type(filter_options);
 
-		string_list_append(&filter_options->filter_spec, "+");
+		strbuf_addch(&filter_options->filter_spec, '+');
 		filter_spec_append_urlencode(filter_options, arg);
 		ALLOC_GROW_BY(filter_options->sub, filter_options->sub_nr, 1,
 			      filter_options->sub_alloc);
@@ -300,31 +300,18 @@ int opt_parse_list_objects_filter(const struct option *opt,
 
 const char *list_objects_filter_spec(struct list_objects_filter_options *filter)
 {
-	if (!filter->filter_spec.nr)
+	if (!filter->filter_spec.len)
 		BUG("no filter_spec available for this filter");
-	if (filter->filter_spec.nr != 1) {
-		struct strbuf concatted = STRBUF_INIT;
-		strbuf_add_separated_string_list(
-			&concatted, "", &filter->filter_spec);
-		string_list_clear(&filter->filter_spec, /*free_util=*/0);
-		string_list_append_nodup(
-			&filter->filter_spec, strbuf_detach(&concatted, NULL));
-	}
-
-	return filter->filter_spec.items[0].string;
+	return filter->filter_spec.buf;
 }
 
 const char *expand_list_objects_filter_spec(
 	struct list_objects_filter_options *filter)
 {
 	if (filter->choice == LOFC_BLOB_LIMIT) {
-		struct strbuf expanded_spec = STRBUF_INIT;
-		strbuf_addf(&expanded_spec, "blob:limit=%lu",
+		strbuf_release(&filter->filter_spec);
+		strbuf_addf(&filter->filter_spec, "blob:limit=%lu",
 			    filter->blob_limit_value);
-		string_list_clear(&filter->filter_spec, /*free_util=*/0);
-		string_list_append_nodup(
-			&filter->filter_spec,
-			strbuf_detach(&expanded_spec, NULL));
 	}
 
 	return list_objects_filter_spec(filter);
@@ -337,7 +324,7 @@ void list_objects_filter_release(
 
 	if (!filter_options)
 		return;
-	string_list_clear(&filter_options->filter_spec, /*free_util=*/0);
+	strbuf_release(&filter_options->filter_spec);
 	free(filter_options->sparse_oid_name);
 	for (sub = 0; sub < filter_options->sub_nr; sub++)
 		list_objects_filter_release(&filter_options->sub[sub]);
@@ -398,8 +385,8 @@ void partial_clone_get_default_filter_spec(
 	if (!promisor || !promisor->partial_clone_filter)
 		return;
 
-	string_list_append(&filter_options->filter_spec,
-			   promisor->partial_clone_filter);
+	strbuf_addstr(&filter_options->filter_spec,
+		      promisor->partial_clone_filter);
 	gently_parse_list_objects_filter(filter_options,
 					 promisor->partial_clone_filter,
 					 &errbuf);
@@ -411,14 +398,12 @@ void list_objects_filter_copy(
 	const struct list_objects_filter_options *src)
 {
 	int i;
-	struct string_list_item *item;
 
 	/* Copy everything. We will overwrite the pointers shortly. */
 	memcpy(dest, src, sizeof(struct list_objects_filter_options));
 
-	string_list_init_dup(&dest->filter_spec);
-	for_each_string_list_item(item, &src->filter_spec)
-		string_list_append(&dest->filter_spec, item->string);
+	strbuf_init(&dest->filter_spec, 0);
+	strbuf_addbuf(&dest->filter_spec, &src->filter_spec);
 	dest->sparse_oid_name = xstrdup_or_null(src->sparse_oid_name);
 
 	ALLOC_ARRAY(dest->sub, dest->sub_alloc);
diff --git a/list-objects-filter-options.h b/list-objects-filter-options.h
index 2720f7dba8..7eeadab2dd 100644
--- a/list-objects-filter-options.h
+++ b/list-objects-filter-options.h
@@ -35,7 +35,7 @@ struct list_objects_filter_options {
 	 * To get the raw filter spec given by the user, use the result of
 	 * list_objects_filter_spec().
 	 */
-	struct string_list filter_spec;
+	struct strbuf filter_spec;
 
 	/*
 	 * 'choice' is determined by parsing the filter-spec.  This indicates
@@ -69,7 +69,7 @@ struct list_objects_filter_options {
 	 */
 };
 
-#define LIST_OBJECTS_FILTER_INIT { .filter_spec = STRING_LIST_INIT_DUP }
+#define LIST_OBJECTS_FILTER_INIT { .filter_spec = STRBUF_INIT }
 void list_objects_filter_init(struct list_objects_filter_options *filter_options);
 
 /*