diff --git a/.github/workflows/android.yml b/.github/workflows/android.yml
index c476bc8..3ad22f7 100644
--- a/.github/workflows/android.yml
+++ b/.github/workflows/android.yml
@@ -19,7 +19,7 @@ jobs:
     - name: Build
       run: |
         cd android
-        ./gradlew assembleRelease
+        ANDROID_NDK_HOME=$ANDROID_SDK_ROOT/ndk-bundle ./gradlew assembleRelease
 
     - name: Upload artifacts
       uses: actions/upload-artifact@v1
diff --git a/android/README.md b/android/README.md
index 382a4d2..8ad9760 100644
--- a/android/README.md
+++ b/android/README.md
@@ -6,7 +6,7 @@ Prebuilt APKs are [here](https://github.com/kichikuou/xsystem35-sdl2/releases).
 ## Build
 Prerequisites:
 - CMake >=3.13
-- Android SDK >=26
+- Android SDK >=28
 - Android NDK >=r15c
 
 ### Using Android Studio
@@ -19,7 +19,8 @@ Example build instructions (for Debian Stretch):
 ```sh
 # Install necessary packages
 sudo apt install git wget unzip default-jdk-headless ninja-build
-sudo apt -t stretch-backports install cmake
+wget https://github.com/Kitware/CMake/releases/download/v3.13.5/cmake-3.13.5-Linux-x86_64.sh
+sudo sh cmake-3.13.5-Linux-x86_64.sh --skip-license --prefix=/usr/local
 
 # Install Android SDK / NDK
 export ANDROID_HOME=$HOME/android-sdk
@@ -29,6 +30,7 @@ wget https://dl.google.com/android/repository/sdk-tools-linux-4333796.zip
 unzip sdk-tools-linux-4333796.zip -d $ANDROID_HOME
 yes |$ANDROID_HOME/tools/bin/sdkmanager --licenses
 $ANDROID_HOME/tools/bin/sdkmanager ndk-bundle
+export ANDROID_NDK_HOME=$ANDROID_HOME/ndk-bundle
 
 # Check out and build xsystem35
 git clone https://github.com/kichikuou/xsystem35-sdl2.git
diff --git a/android/app/build.gradle b/android/app/build.gradle
index a771f1f..38c2664 100644
--- a/android/app/build.gradle
+++ b/android/app/build.gradle
@@ -1,4 +1,4 @@
-def buildAsLibrary = project.hasProperty('BUILD_AS_LIBRARY');
+def buildAsLibrary = project.hasProperty('BUILD_AS_LIBRARY')
 def buildAsApplication = !buildAsLibrary
 if (buildAsApplication) {
     apply plugin: 'com.android.application'
@@ -9,13 +9,13 @@ else {
 apply plugin: 'kotlin-android'
 
 android {
-    compileSdkVersion 26
+    compileSdkVersion 28
     defaultConfig {
         if (buildAsApplication) {
             applicationId "io.github.kichikuou.xsystem35"
         }
         minSdkVersion 19
-        targetSdkVersion 26
+        targetSdkVersion 28
         versionCode 4
         versionName "0.2.1"
         externalNativeBuild {
diff --git a/android/build.gradle b/android/build.gradle
index 6e1d82a..759c67c 100644
--- a/android/build.gradle
+++ b/android/build.gradle
@@ -1,13 +1,13 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.3.61'
+    ext.kotlin_version = '1.3.72'
     repositories {
         jcenter()
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.2.0'
+        classpath 'com.android.tools.build:gradle:4.0.1'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong
diff --git a/android/gradle/wrapper/gradle-wrapper.properties b/android/gradle/wrapper/gradle-wrapper.properties
index f9b3be2..304acfe 100644
--- a/android/gradle/wrapper/gradle-wrapper.properties
+++ b/android/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
-#Mon Oct 23 13:51:26 PDT 2017
+#Mon Aug 10 12:24:31 JST 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.2-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip