diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 61552e89bd89df8925d8e13ced1c645923c0ef79..482e241c963915fc846f06b09950f4533a86b1c6 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4952,6 +4952,7 @@ static int nfsd4_check_conflicting_opens(struct nfs4_client *clp,
 		writes--;
 	if (fp->fi_fds[O_RDWR])
 		writes--;
+	WARN_ON_ONCE(writes < 0);
 	if (writes > 0)
 		return -EAGAIN;
 	spin_lock(&fp->fi_lock);