diff --git a/lib/modules/datasource/index.ts b/lib/modules/datasource/index.ts
index dd0d5f198228cc..7b08df36a839fa 100644
--- a/lib/modules/datasource/index.ts
+++ b/lib/modules/datasource/index.ts
@@ -278,6 +278,7 @@ async function fetchReleases(
   const datasource = getDatasourceFor(datasourceName);
   // istanbul ignore if: needs test
   if (!datasource) {
+    logger.warn({ datasource: datasourceName }, 'Unknown datasource');
     return null;
   }
   registryUrls = resolveRegistryUrls(