diff --git a/shared/editor/nodes/Attachment.tsx b/shared/editor/nodes/Attachment.tsx
index 3e889e4fa..e0e51c916 100644
--- a/shared/editor/nodes/Attachment.tsx
+++ b/shared/editor/nodes/Attachment.tsx
@@ -86,7 +86,7 @@ export default class Attachment extends Node {
         onMouseDown={this.handleSelect(props)}
         context={
           node.attrs.href ? (
-            bytesToHumanReadable(node.attrs.size)
+            bytesToHumanReadable(node.attrs.size || "0")
           ) : (
             <>
               <Trans>Uploading</Trans>…