diff --git a/lib/manager/composer/artifacts.js b/lib/manager/composer/artifacts.js
index 9068b0082618d19b32af89a8aa18683f899b23b6..9cefb21a3aaecfd6a0f2f0a82bc22992b8837b65 100644
--- a/lib/manager/composer/artifacts.js
+++ b/lib/manager/composer/artifacts.js
@@ -77,7 +77,7 @@ async function getArtifacts(
             }
           }
         }
-      } else {
+      } else if (config.registryUrls) {
         logger.warn(
           { registryUrls: config.registryUrls },
           'Non-array composer registryUrls'