diff --git a/src/ComposerFileStorage.php b/src/ComposerFileStorage.php
index 41602c8..c36858c 100644
--- a/src/ComposerFileStorage.php
+++ b/src/ComposerFileStorage.php
@@ -53,8 +53,30 @@ public static function create(string $url, Config $config): self
     {
         $basePath = implode(DIRECTORY_SEPARATOR, [
             static::basePath($config),
-            preg_replace('/[^[:alnum:]\.]/', '-', $url),
+            static::escapeUrl($url),
         ]);
         return new static($basePath);
     }
+
+    /**
+     * Converts a repository URL to a unique directory name.
+     *
+     * @param string $url
+     *   A repository URL.
+     *
+     * @return string
+     *   A version of the URL suitable to use as the name of the persistent
+     *   storage directory.
+     */
+    public static function escapeUrl(string $url): string
+    {
+        $escapedUrl = preg_replace('/[^[:alnum:]\.]/', '-', $url);
+        // Append a partial hash of the unescaped URL, to prevent URLs like
+        // `https://www.site.coop.info/packages` from colliding with
+        // `https://www.site.coop/info/packages`, whilst keeping the directory
+        // names easily distinguishable.
+        $hashedUrl = hash('sha256', $url);
+
+        return $escapedUrl . '-' . substr($hashedUrl, 0, 8);
+    }
 }
diff --git a/tests/ComposerFileStorageTest.php b/tests/ComposerFileStorageTest.php
index b1208d1..711f0ee 100644
--- a/tests/ComposerFileStorageTest.php
+++ b/tests/ComposerFileStorageTest.php
@@ -50,23 +50,40 @@ public function testBasePath(): void
         $this->assertSame($expectedPath, ComposerFileStorage::basePath($config));
     }
 
+    /**
+     * @covers ::escapeUrl
+     */
+    public function testEscapeUrl(): void
+    {
+        // Ensure that two very similar URLs are converted into unique, but
+        // readable, directory names.
+        $url1 = ComposerFileStorage::escapeUrl('https://site.coop/info/packages');
+        $url2 = ComposerFileStorage::escapeUrl('https://site.coop.info/packages');
+
+        $this->assertNotSame($url1, $url2);
+        $this->assertMatchesRegularExpression('/^https---site\.coop-info-packages-[a-z0-9]{8}$/', $url1);
+        $this->assertMatchesRegularExpression('/^https---site\.coop\.info-packages-[a-z0-9]{8}$/', $url2);
+    }
+
     /**
      * @covers ::__construct
      * @covers ::create
      *
      * @depends testBasePath
+     * @depends testEscapeUrl
      */
     public function testCreate(): void
     {
+        $url = 'https://example.net/packages';
         $config = new Config();
 
         $basePath = implode(DIRECTORY_SEPARATOR, [
            ComposerFileStorage::basePath($config),
-            'https---example.net-packages',
+           ComposerFileStorage::escapeUrl($url),
         ]);
         $this->assertDirectoryDoesNotExist($basePath);
 
-        ComposerFileStorage::create('https://example.net/packages', $config);
+        ComposerFileStorage::create($url, $config);
         $this->assertDirectoryExists($basePath);
     }
 }