diff --git a/src/Vervis/Actor/Group.hs b/src/Vervis/Actor/Group.hs
index 22ab360..4d6c414 100644
--- a/src/Vervis/Actor/Group.hs
+++ b/src/Vervis/Actor/Group.hs
@@ -200,7 +200,7 @@ groupAccept now groupID (Verse authorIdMsig body) accept = do
                 case (collab, acceptDB) of
                     (Left (fulfillsID, Left recipID), Left (_, _, acceptID)) -> do
                         maybeAccept <- lift $ insertUnique $ CollabRecipLocalAccept recipID fulfillsID acceptID
-                        unless (isNothing maybeAccept) $
+                        unless (isJust maybeAccept) $
                             throwE "This Invite already has an Accept by recip"
                     (Left (fulfillsID, Right recipID), Right (_, _, acceptID)) -> do
                         maybeAccept <- lift $ insertUnique $ CollabRecipRemoteAccept recipID fulfillsID acceptID