diff --git a/lib/manager/npm/monorepos.js b/lib/manager/npm/monorepos.js
index b01f243ad0ec4bc757f391830a01b0007e660456..fbf3079092dc90dbfff9bc158a4eca7dce1f8f91 100644
--- a/lib/manager/npm/monorepos.js
+++ b/lib/manager/npm/monorepos.js
@@ -8,32 +8,36 @@ module.exports = {
 
 async function checkMonorepos(config) {
   const monorepoPackages = [];
-  let workspaceDir;
+  logger.debug('checkMonorepos()');
+  logger.trace({ config });
   // yarn workspaces
-  let workspaces = [];
   for (const packageFile of config.packageFiles) {
     if (
       packageFile.packageFile &&
       packageFile.packageFile.endsWith('package.json') &&
       packageFile.content.workspaces
     ) {
-      workspaceDir = path.dirname(packageFile.packageFile);
-      logger.info(`workspaceDir=${config.workspaceDir}`);
-      ({ workspaces } = packageFile.content);
-    }
-  }
-  if (workspaces.length) {
-    logger.debug({ workspaces }, 'Found yarn workspaces');
-  }
-  for (const workspace of workspaces) {
-    const basePath = upath.join(workspaceDir, workspace);
-    logger.info(`basePath=${basePath}`);
-    for (const packageFile of config.packageFiles) {
-      if (minimatch(path.dirname(packageFile.packageFile), basePath)) {
-        logger.info(`Matched ${packageFile.packageFile}`);
-        const depName = packageFile.content.name;
-        monorepoPackages.push(depName);
-        packageFile.workspaceDir = workspaceDir;
+      const workspaceDir = path.dirname(packageFile.packageFile);
+      const { workspaces } = packageFile.content;
+      if (workspaces.length) {
+        logger.info(
+          { packageFile: packageFile.packageFile, workspaces },
+          'Found yarn workspaces'
+        );
+        for (const workspace of workspaces) {
+          const basePath = upath.join(workspaceDir, workspace);
+          logger.debug(`basePath=${basePath}`);
+          for (const innerPackageFile of config.packageFiles) {
+            if (
+              minimatch(path.dirname(innerPackageFile.packageFile), basePath)
+            ) {
+              logger.debug(`Matched ${innerPackageFile.packageFile}`);
+              const depName = innerPackageFile.content.name;
+              monorepoPackages.push(depName);
+              innerPackageFile.workspaceDir = workspaceDir;
+            }
+          }
+        }
       }
     }
   }