diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/ClassBody.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/ClassBody.js
index 7c0164ed3e..e80966618b 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/ClassBody.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/ClassBody.js
@@ -60,7 +60,7 @@ export function ClassBody(node, context) {
 			const _key = (key.type === 'PrivateIdentifier' ? '#' : '') + name;
 			const field = fields.get(_key);
 
-			if (field.length > 1 || (field.length === 1 && field[0] !== 'prop')) {
+			if (field && (field.length > 1 || (field.length === 1 && field[0] !== 'prop'))) {
 				e.duplicate_class_field(node, _key);
 			}