diff --git a/src/SPC/builder/Extension.php b/src/SPC/builder/Extension.php
index 2ab50f98..43e0a5e8 100644
--- a/src/SPC/builder/Extension.php
+++ b/src/SPC/builder/Extension.php
@@ -275,6 +275,10 @@ class Extension
      */
     public function buildShared(): void
     {
+        if (file_exists(BUILD_MODULES_PATH . '/' . $this->getName() . '.so')) {
+            logger()->info('extension ' . $this->getName() . ' already built, skipping');
+            return;
+        }
         match (PHP_OS_FAMILY) {
             'Darwin', 'Linux' => $this->buildUnixShared(),
             default => throw new WrongUsageException(PHP_OS_FAMILY . ' build shared extensions is not supported yet'),
diff --git a/src/SPC/builder/extension/bz2.php b/src/SPC/builder/extension/bz2.php
index 88f22e56..ee3f2996 100644
--- a/src/SPC/builder/extension/bz2.php
+++ b/src/SPC/builder/extension/bz2.php
@@ -24,4 +24,9 @@ class bz2 extends Extension
         FileSystem::replaceFileRegex(SOURCE_PATH . '/php-src/configure', '/-lbz2/', $this->getLibFilesString() . $frameworks);
         return true;
     }
+
+    public function getUnixConfigureArg(bool $shared = false): string
+    {
+        return $shared ? '--with-bz2=' . BUILD_ROOT_PATH : '';
+    }
 }