diff --git a/src/DrupalFinder.php b/src/DrupalFinder.php
index 642ea8f..fd6ef86 100644
--- a/src/DrupalFinder.php
+++ b/src/DrupalFinder.php
@@ -75,6 +75,12 @@ private function shiftPathUp($path)
     {
         $parent = dirname($path);
 
+        // If $path did not contain any parents, it may be a relative path:
+        // normalize it to the realpath first.
+        if ($parent === '.' && ($realpath = realpath($path))) {
+            $parent = dirname($realpath);
+        }
+
         return in_array($parent, ['.', $path]) ? false : $parent;
     }
 
diff --git a/tests/Drupal8FinderTest.php b/tests/Drupal8FinderTest.php
index ad84954..c4292d2 100644
--- a/tests/Drupal8FinderTest.php
+++ b/tests/Drupal8FinderTest.php
@@ -247,6 +247,18 @@ public function testDrupalWithCustomVendor()
         $this->assertSame($root . '/vendor-foo', realpath($this->finder->getVendorDir()));
     }
 
+    public function testDrupalComposerWithRelativeRoot()
+    {
+        $root = $this->tempdir(sys_get_temp_dir());
+        $fileStructure = ['drupal' => $this->getDrupalComposerStructure()];
+        $this->dumpToFileSystem($fileStructure, $root);
+
+        $cwd = getcwd();
+        chdir($root . '/drupal');
+        $this->assertTrue($this->finder->locateRoot('web'));
+        chdir($cwd);
+    }
+
     /**
      * @param $fileStructure
      */