diff --git a/core/lib/Drupal/Core/Asset/Exception/ExtensionDoesNotExistEception.php b/core/lib/Drupal/Core/Asset/Exception/ExtensionDoesNotExistException.php
similarity index 65%
rename from core/lib/Drupal/Core/Asset/Exception/ExtensionDoesNotExistEception.php
rename to core/lib/Drupal/Core/Asset/Exception/ExtensionDoesNotExistException.php
index cb5b25e..1537bf5 100644
--- a/core/lib/Drupal/Core/Asset/Exception/ExtensionDoesNotExistEception.php
+++ b/core/lib/Drupal/Core/Asset/Exception/ExtensionDoesNotExistException.php
@@ -3,7 +3,7 @@
 namespace Drupal\Core\Asset\Exception;
 
 /**
- * Defines a custom exception if a theme is not installed.
+ * Defines a custom exception if an extension is not installed.
  */
 class ExtensionDoesNotExistException extends \RuntimeException {
 
diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
index 730a1e3..93e011e 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
@@ -97,7 +97,7 @@ public function buildByExtension($extension) {
         $extension_type = 'theme';
       }
       else {
-        throw new ExtensionDoesNotExistException(sprintf("Theme extension '%s' could not be found because its extension '%s' is not installed",  $extension));
+        throw new ExtensionDoesNotExistException(sprintf("The extension '%s' is not installed.", $extension));
       }
       $path = $this->drupalGetPath($extension_type, $extension);
     }
diff --git a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
index f2f8127..bd519ed 100644
--- a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
@@ -175,15 +175,22 @@ public function testInvalidLibrariesFile() {
   }
 
   /**
-   * Tests that an exception is thrown when a theme is not installed.
+   * Tests that an exception is thrown when the extension is not a valid
+   * module or theme.
    *
-   * @expectedException \InvalidArgumentException
+   * @expectedException \Drupal\Core\Asset\Exception\ExtensionDoesNotExistException
    *
    * @covers ::buildByExtension
    */
-  public function testUnistalledTheme() {
+  public function testMissingExtension() {
     $this->moduleHandler->expects($this->atLeastOnce())
       ->method('moduleExists')
+      ->with('uninstalled_theme')
+      ->will($this->returnValue(FALSE));
+
+    $this->themeHandler->expects($this->atLeastOnce())
+      ->method('themeExists')
+      ->with('uninstalled_theme')
       ->will($this->returnValue(FALSE));
 
     $this->libraryDiscoveryParser->buildByExtension('uninstalled_theme');