diff --git a/src/AssetService.php b/src/AssetService.php
index f467b06..b9c5c01 100644
--- a/src/AssetService.php
+++ b/src/AssetService.php
@@ -119,5 +119,7 @@ protected function getType($path)
         if (isset($this->types[$ext])) {
             return $this->types[$ext];
         }
+
+        return 'application/octet-stream';
     }
 }
diff --git a/tests/src/AssetServiceTest.php b/tests/src/AssetServiceTest.php
index 51060dc..6c8b914 100644
--- a/tests/src/AssetServiceTest.php
+++ b/tests/src/AssetServiceTest.php
@@ -31,7 +31,7 @@ public function testGetAsset_noVendorPackage()
     {
         $asset = $this->service->getAsset('no-vendor', 'no-package', 'style.css');
         $this->assertNull($asset->path);
-        $this->assertNull($asset->type);
+        $this->assertEquals('application/octet-stream', $asset->type);
     }
 
     public function testGetAsset_noType()
@@ -41,6 +41,6 @@ public function testGetAsset_noType()
         $expect = $this->asset_dir . DIRECTORY_SEPARATOR . 'fake.txt';
         $this->assertSame($expect, $asset->path);
 
-        $this->assertNull($asset->type);
+        $this->assertEquals('application/octet-stream', $asset->type);
     }
 }