diff --git a/src/functions.php b/src/functions.php
index f578e65..9c03bf5 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -2,63 +2,70 @@
 
 namespace FastRoute;
 
-/**
- * @param callable $routeDefinitionCallback
- * @param array $options
- *
- * @return Dispatcher
- */
-function simpleDispatcher(callable $routeDefinitionCallback, array $options = []) {
-    $options += [
-        'routeParser' => 'FastRoute\\RouteParser\\Std',
-        'dataGenerator' => 'FastRoute\\DataGenerator\\GroupCountBased',
-        'dispatcher' => 'FastRoute\\Dispatcher\\GroupCountBased',
-    ];
+if ( ! function_exists('\FastRoute\simpleDispatcher') ) {
+    /**
+     * @param callable $routeDefinitionCallback
+     * @param array    $options
+     *
+     * @return Dispatcher
+     */
+    function simpleDispatcher( callable $routeDefinitionCallback, array $options = [ ] )
+    {
+        $options += [
+            'routeParser'   => 'FastRoute\\RouteParser\\Std',
+            'dataGenerator' => 'FastRoute\\DataGenerator\\GroupCountBased',
+            'dispatcher'    => 'FastRoute\\Dispatcher\\GroupCountBased',
+        ];
 
-    $routeCollector = new RouteCollector(
-        new $options['routeParser'], new $options['dataGenerator']
-    );
-    $routeDefinitionCallback($routeCollector);
+        $routeCollector = new RouteCollector(
+            new $options[ 'routeParser' ], new $options[ 'dataGenerator' ]
+        );
+        $routeDefinitionCallback( $routeCollector );
 
-    return new $options['dispatcher']($routeCollector->getData());
+        return new $options[ 'dispatcher' ]( $routeCollector->getData() );
+    }
 }
 
-/**
- * @param callable $routeDefinitionCallback
- * @param array $options
- *
- * @return Dispatcher
- */
-function cachedDispatcher(callable $routeDefinitionCallback, array $options = []) {
-    $options += [
-        'routeParser' => 'FastRoute\\RouteParser\\Std',
-        'dataGenerator' => 'FastRoute\\DataGenerator\\GroupCountBased',
-        'dispatcher' => 'FastRoute\\Dispatcher\\GroupCountBased',
-        'cacheDisabled' => false,
-    ];
+if ( ! function_exists('\FastRoute\cachedDispatcher') ) {
+    /**
+     * @param callable $routeDefinitionCallback
+     * @param array    $options
+     *
+     * @return Dispatcher
+     */
+    function cachedDispatcher( callable $routeDefinitionCallback, array $options = [ ] )
+    {
+        $options += [
+            'routeParser'   => 'FastRoute\\RouteParser\\Std',
+            'dataGenerator' => 'FastRoute\\DataGenerator\\GroupCountBased',
+            'dispatcher'    => 'FastRoute\\Dispatcher\\GroupCountBased',
+            'cacheDisabled' => false,
+        ];
 
-    if (!isset($options['cacheFile'])) {
-        throw new \LogicException('Must specify "cacheFile" option');
-    }
+        if (!isset( $options[ 'cacheFile' ] )) {
+            throw new \LogicException( 'Must specify "cacheFile" option' );
+        }
 
-    if (!$options['cacheDisabled'] && file_exists($options['cacheFile'])) {
-        $dispatchData = require $options['cacheFile'];
-        if (!is_array($dispatchData)) {
-            throw new \RuntimeException('Invalid cache file "' . $options['cacheFile'] . '"');
+        if (!$options[ 'cacheDisabled' ] && file_exists( $options[ 'cacheFile' ] )) {
+            $dispatchData = require $options[ 'cacheFile' ];
+            if (!is_array( $dispatchData )) {
+                throw new \RuntimeException( 'Invalid cache file "' . $options[ 'cacheFile' ] . '"' );
+            }
+
+            return new $options[ 'dispatcher' ]( $dispatchData );
         }
-        return new $options['dispatcher']($dispatchData);
-    }
 
-    $routeCollector = new RouteCollector(
-        new $options['routeParser'], new $options['dataGenerator']
-    );
-    $routeDefinitionCallback($routeCollector);
+        $routeCollector = new RouteCollector(
+            new $options[ 'routeParser' ], new $options[ 'dataGenerator' ]
+        );
+        $routeDefinitionCallback( $routeCollector );
 
-    $dispatchData = $routeCollector->getData();
-    file_put_contents(
-        $options['cacheFile'],
-        '<?php return ' . var_export($dispatchData, true) . ';'
-    );
+        $dispatchData = $routeCollector->getData();
+        file_put_contents(
+            $options[ 'cacheFile' ],
+            '<?php return ' . var_export( $dispatchData, true ) . ';'
+        );
 
-    return new $options['dispatcher']($dispatchData);
+        return new $options[ 'dispatcher' ]( $dispatchData );
+    }
 }