diff --git a/src/DrupalFinder.php b/src/DrupalFinder.php
index 98bb0c9..683440f 100644
--- a/src/DrupalFinder.php
+++ b/src/DrupalFinder.php
@@ -119,6 +119,11 @@ protected function isValidRoot($path)
                             $this->vendorDir = $this->composerRoot . '/vendor';
                         }
                     }
+                } elseif (!empty($json['extra']['drupal-web-dir'])) {
+                    $web_prefix = $json['extra']['drupal-web-dir'];
+                    $this->composerRoot = $path;
+                    $this->drupalRoot = $path . '/' . $web_prefix;
+                    $this->vendorDir = $path . '/vendor';
                 }
             }
         }