diff --git a/android/build.gradle b/android/build.gradle
old mode 100755
new mode 100644
index fa6963f8..083f01ba
--- a/android/build.gradle
+++ b/android/build.gradle
@@ -19,7 +19,14 @@ buildscript {
 }
 
 apply plugin: 'com.android.library'
-apply plugin: 'kotlin-android'
+// AGP 9 ships built-in Kotlin support and registers the `kotlin` extension
+// itself. Applying the Kotlin plugin on top of it fails configuration with
+// "Cannot add extension with name 'kotlin'". Only apply it when nothing has
+// registered that extension yet.
+if (project.extensions.findByName('kotlin') == null) {
+    apply plugin: 'kotlin-android'
+}
+
 apply plugin: 'kotlin-android-extensions'
 
 def DEFAULT_COMPILE_SDK_VERSION = 28