diff --git a/components/SelectDropdown.vue b/components/SelectDropdown.vue
index fb67d24..0e40e82 100644
--- a/components/SelectDropdown.vue
+++ b/components/SelectDropdown.vue
@@ -163,7 +163,7 @@ function keyBackspace(event: KeyboardEvent) {
 			return;
 		}
 		if (props.multi) {
-			selectedIds.value.delete(lastId);
+			selectedIds.value = new Set(selectedIds.value).difference(new Set([lastId]));
 		} else {
 			selectedIds.value = new Set();
 		}
@@ -175,9 +175,9 @@ function toggleActive(event: MouseEvent | KeyboardEvent) {
 	if (activeId.value !== undefined) {
 		if (props.multi) {
 			if (selectedIds.value.has(activeId.value)) {
-				selectedIds.value.delete(activeId.value);
+				selectedIds.value = new Set(selectedIds.value).difference(new Set([activeId.value]));
 			} else {
-				selectedIds.value.add(activeId.value);
+				selectedIds.value = new Set(selectedIds.value).union(new Set([activeId.value]));
 			}
 		} else {
 			selectedIds.value = new Set([activeId.value]);