diff --git a/backend/internal/latest/poller.go b/backend/internal/latest/poller.go
index cfbdea8..8f31abc 100644
--- a/backend/internal/latest/poller.go
+++ b/backend/internal/latest/poller.go
@@ -124,7 +124,13 @@ func (p *Poller) storeCover(ctx context.Context, sr store.Series, sourceURL stri
 // absent, the entry's Fallback decides whether plain TLS may take over. One
 // routing rule for the poll and the acquirer, so the two cannot drift apart.
 func fetcherFor(site string, browser, tls Fetcher) Fetcher {
-	s := sites[site]
+	s, known := sites[site]
+	if !known {
+		// No registry entry means nothing to fetch or parse; fail closed even
+		// though the only caller gates first, so a future caller that skips
+		// the gate cannot hand an arbitrary https URL to the TLS fetcher.
+		return nil
+	}
 	if s.Browser == nil {
 		return tls
 	}
diff --git a/backend/internal/latest/poller_test.go b/backend/internal/latest/poller_test.go
index d76a2b4..6bbb6e5 100644
--- a/backend/internal/latest/poller_test.go
+++ b/backend/internal/latest/poller_test.go
@@ -959,6 +959,8 @@ func TestFetcherForRoutesNovelSites(t *testing.T) {
 		// browser-less deployment: kagane is nothing, novelfull degrades to TLS
 		{"kagane", nil, tls, nil},
 		{"novelfull", nil, tls, tls},
+		// unknown site: fail closed — nothing to fetch or parse
+		{"mangadex", browser, tls, nil},
 	}
 	for _, tc := range cases {
 		t.Run(tc.site, func(t *testing.T) {