diff --git a/framework/yii/web/AssetConverter.php b/framework/yii/web/AssetConverter.php
index 75a3106..3b654e5 100644
--- a/framework/yii/web/AssetConverter.php
+++ b/framework/yii/web/AssetConverter.php
@@ -47,17 +47,46 @@ class AssetConverter extends Component implements AssetConverterInterface
 				list ($ext, $command) = $this->commands[$ext];
 				$result = substr($asset, 0, $pos + 1) . $ext;
 				if (@filemtime("$basePath/$result") < filemtime("$basePath/$asset")) {
-					$output = [];
-					$command = strtr($command, [
-						'{from}' => escapeshellarg("$basePath/$asset"),
-						'{to}' => escapeshellarg("$basePath/$result"),
-					]);
-					exec($command, $output);
-					Yii::trace("Converted $asset into $result: " . implode("\n", $output), __METHOD__);
+					$this->runCommand($command, $basePath, $asset, $result);
 				}
 				return $result;
 			}
 		}
 		return $asset;
 	}
+
+	/**
+	 * Runs a command to convert asset files.
+	 * @param string $command the command to run
+	 * @param string $basePath asset base path and command working directory
+	 * @param string $asset the name of the asset file
+	 * @param string $result the name of the file to be generated by the converter command
+	 * @return bool true on success, false on failure. Failures will be logged.
+	 */
+	protected function runCommand($command, $basePath, $asset, $result)
+	{
+		$command = strtr($command, [
+			'{from}' => escapeshellarg("$basePath/$asset"),
+			'{to}' => escapeshellarg("$basePath/$result"),
+		]);
+		$descriptor = array(
+			1 => array('pipe', 'w'),
+			2 => array('pipe', 'w'),
+		);
+		$pipes = array();
+		$proc = proc_open($command, $descriptor, $pipes, $basePath);
+		$stdout = stream_get_contents($pipes[1]);
+		$stderr = stream_get_contents($pipes[2]);
+		foreach($pipes as $pipe) {
+			fclose($pipe);
+		}
+		$status = proc_close($proc);
+
+		if ($status !== 0) {
+			Yii::error("AssetConverter command '$command' failed with exit code $status:\nSTDOUT:\n$stdout\nSTDERR:\n$stderr\n");
+		} else {
+			Yii::trace("Converted $asset into $result:\nSTDOUT:\n$stdout\nSTDERR:\n$stderr", __METHOD__);
+		}
+		return $status === 0;
+	}
 }
diff --git a/tests/unit/framework/web/AssetConverterTest.php b/tests/unit/framework/web/AssetConverterTest.php
new file mode 100644
index 0000000..54669b3
--- /dev/null
+++ b/tests/unit/framework/web/AssetConverterTest.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * @author Carsten Brandt <mail@cebe.cc>
+ */
+
+namespace yiiunit\framework\web;
+use yii\web\AssetConverter;
+
+/**
+ * @group web
+ */
+class AssetConverterTest extends \yiiunit\TestCase
+{
+	protected function setUp()
+	{
+		parent::setUp();
+		$this->mockApplication();
+	}
+
+
+	public function testConvert()
+	{
+		$tmpPath = \Yii::$app->runtimePath . '/assetConverterTest';
+		if (!is_dir($tmpPath)) {
+			mkdir($tmpPath, 0777, true);
+		}
+		file_put_contents($tmpPath . '/test.php', <<<EOF
+<?php
+
+echo "Hello World!\n";
+echo "Hello Yii!";
+EOF
+		);
+
+		$converter = new AssetConverter();
+		$converter->commands['php'] = ['txt', 'php {from} > {to}'];
+		$this->assertEquals('test.txt', $converter->convert('test.php', $tmpPath));
+
+		$this->assertTrue(file_exists($tmpPath . '/test.txt'), 'Failed asserting that asset output file exists.');
+		$this->assertEquals("Hello World!\nHello Yii!", file_get_contents($tmpPath . '/test.txt'));
+	}
+}
\ No newline at end of file