diff --git a/src/Composer/Package/Version/VersionParser.php b/src/Composer/Package/Version/VersionParser.php
index 3925e7e65..d546b2655 100644
--- a/src/Composer/Package/Version/VersionParser.php
+++ b/src/Composer/Package/Version/VersionParser.php
@@ -176,12 +176,13 @@ class VersionParser
      * @param string $branch Branch name (e.g. 2.1.x-dev)
      * @return string|false Numeric prefix if present (e.g. 2.1.) or false
      */
-    public function parseNumericAliasPrefix($branch) {
-        if(preg_match('/^(?<version>(\d+\\.)*\d+).x-dev$/i', $branch, $matches)) {
+    public function parseNumericAliasPrefix($branch)
+    {
+        if (preg_match('/^(?<version>(\d+\\.)*\d+)(?:\.x)?-dev$/i', $branch, $matches)) {
             return $matches['version'].".";
-        } else {
-            return false;
         }
+
+        return false;
     }
 
     /**
diff --git a/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php b/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php
index 4b98ae26d..1491571a1 100644
--- a/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php
+++ b/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php
@@ -139,6 +139,17 @@ class ArrayLoaderTest extends \PHPUnit_Framework_TestCase
         $this->assertInstanceOf('Composer\Package\AliasPackage', $package);
         $this->assertEquals('1.0.x-dev', $package->getPrettyVersion());
 
+        $config = array(
+            'name' => 'A',
+            'version' => 'dev-master',
+            'extra' => array('branch-alias' => array('dev-master' => '1.0-dev')),
+        );
+
+        $package = $this->loader->load($config);
+
+        $this->assertInstanceOf('Composer\Package\AliasPackage', $package);
+        $this->assertEquals('1.0.x-dev', $package->getPrettyVersion());
+
         $config = array(
             'name' => 'B',
             'version' => '4.x-dev',
@@ -150,6 +161,17 @@ class ArrayLoaderTest extends \PHPUnit_Framework_TestCase
         $this->assertInstanceOf('Composer\Package\AliasPackage', $package);
         $this->assertEquals('4.0.x-dev', $package->getPrettyVersion());
 
+        $config = array(
+            'name' => 'B',
+            'version' => '4.x-dev',
+            'extra' => array('branch-alias' => array('4.x-dev' => '4.0-dev')),
+        );
+
+        $package = $this->loader->load($config);
+
+        $this->assertInstanceOf('Composer\Package\AliasPackage', $package);
+        $this->assertEquals('4.0.x-dev', $package->getPrettyVersion());
+
         $config = array(
             'name' => 'C',
             'version' => '4.x-dev',
diff --git a/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php b/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php
index 2b0829759..32c55bd40 100644
--- a/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php
+++ b/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php
@@ -339,6 +339,20 @@ class ValidatingArrayLoaderTest extends \PHPUnit_Framework_TestCase
                 ),
                 false
             ),
+            array(
+                array(
+                    'name' => 'foo/bar',
+                    'extra' => array(
+                        'branch-alias' => array(
+                            '5.x-dev' => '3.1-dev'
+                        ),
+                    )
+                ),
+                array(
+                    'extra.branch-alias.5.x-dev : the target branch (3.1-dev) is not a valid numeric alias for this version'
+                ),
+                false
+            ),
         );
     }
 }
diff --git a/tests/Composer/Test/Package/Version/VersionParserTest.php b/tests/Composer/Test/Package/Version/VersionParserTest.php
index c52ec1382..13920e2f0 100644
--- a/tests/Composer/Test/Package/Version/VersionParserTest.php
+++ b/tests/Composer/Test/Package/Version/VersionParserTest.php
@@ -67,26 +67,6 @@ class VersionParserTest extends \PHPUnit_Framework_TestCase
         return array_map($createPackage, $data);
     }
 
-    /**
-     * @dataProvider successfulNormalizedVersions
-     */
-    public function testNormalizeSucceeds($input, $expected)
-    {
-        $parser = new VersionParser;
-        $this->assertSame($expected, $parser->normalize($input));
-    }
-
-    public function numericAliasVersions() {
-        return array(
-            array('0.x-dev',        '0.'),
-            array('1.0.x-dev',      '1.0.'),
-            array('1.x-dev',        '1.'),
-            array('1.2.x-dev',      '1.2.'),
-            array('dev-develop',    false),
-            array('dev-master',     false),
-        );
-    }
-
     /**
      * @dataProvider numericAliasVersions
      */
@@ -96,6 +76,29 @@ class VersionParserTest extends \PHPUnit_Framework_TestCase
         $this->assertSame($expected, $parser->parseNumericAliasPrefix($input));
     }
 
+    public function numericAliasVersions()
+    {
+        return array(
+            array('0.x-dev',        '0.'),
+            array('1.0.x-dev',      '1.0.'),
+            array('1.x-dev',        '1.'),
+            array('1.2.x-dev',      '1.2.'),
+            array('1.2-dev',        '1.2.'),
+            array('1-dev',          '1.'),
+            array('dev-develop',    false),
+            array('dev-master',     false),
+        );
+    }
+
+    /**
+     * @dataProvider successfulNormalizedVersions
+     */
+    public function testNormalizeSucceeds($input, $expected)
+    {
+        $parser = new VersionParser;
+        $this->assertSame($expected, $parser->normalize($input));
+    }
+
     public function successfulNormalizedVersions()
     {
         return array(
diff --git a/tests/Composer/Test/Package/Version/VersionSelectorTest.php b/tests/Composer/Test/Package/Version/VersionSelectorTest.php
index fb3a6f666..6feb207a7 100644
--- a/tests/Composer/Test/Package/Version/VersionSelectorTest.php
+++ b/tests/Composer/Test/Package/Version/VersionSelectorTest.php
@@ -113,10 +113,12 @@ class VersionSelectorTest extends \PHPUnit_Framework_TestCase
             array('3.1.2-dev', true, 'dev', '3.1.2-dev'),
             // dev packages with alias inherit the alias
             array('dev-master', true, 'dev', '~2.1@dev', '2.1.x-dev'),
+            array('dev-master', true, 'dev', '~2.1@dev', '2.1-dev'),
             array('dev-master', true, 'dev', '~2.1@dev', '2.1.3.x-dev'),
             array('dev-master', true, 'dev', '~2.0@dev', '2.x-dev'),
             // numeric alias
             array('3.x-dev', true, 'dev', '~3.0@dev', '3.0.x-dev'),
+            array('3.x-dev', true, 'dev', '~3.0@dev', '3.0-dev'),
         );
     }