diff --git a/.travis.yml b/.travis.yml
index fbcce59d..8428ae43 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,9 +4,9 @@ jdk:
 android:
   components:
     - tools
-    - build-tools-25.0.3
+    - build-tools-28.0.3
     - android-21
-    - android-23
+    - android-26
     - extra-android-m2repository
     - sys-img-armeabi-v7a-android-21
 
diff --git a/build.gradle b/build.gradle
index ecf861a3..18c5e0b4 100644
--- a/build.gradle
+++ b/build.gradle
@@ -7,9 +7,10 @@ buildscript {
             url 'https://maven.google.com/'
             name 'Google'
         }
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.3'
+        classpath 'com.android.tools.build:gradle:3.3.2'
         classpath 'nl.javadude.gradle.plugins:license-gradle-plugin:0.7.0'
     }
 }
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 9fdd8f93..93df8e4e 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
-#Wed Jul 03 11:27:59 KST 2019
+#Tue Jul 16 09:35:53 MSK 2019
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.0-all.zip
diff --git a/library/build.gradle b/library/build.gradle
index 74abe217..03c264cc 100644
--- a/library/build.gradle
+++ b/library/build.gradle
@@ -7,14 +7,14 @@ group 'com.anjlab.android.iab.v3'
 version '1.0.44'
 
 android {
-    compileSdkVersion 23
-    buildToolsVersion '25.0.3'
+    compileSdkVersion 26
+    buildToolsVersion '28.0.3'
 
     defaultConfig {
         versionCode 1
         versionName project.version
-        minSdkVersion 8
-        targetSdkVersion 23
+        minSdkVersion 9
+        targetSdkVersion 26
         consumerProguardFiles 'progress-proguard.txt'
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
     }
@@ -33,10 +33,10 @@ android {
 }
 
 dependencies {
-    androidTestCompile 'com.android.support.test:runner:0.5'
-    androidTestCompile 'com.android.support.test:rules:0.5'
-    compile 'com.android.support:support-annotations:25.3.1'
-    compile 'com.android.billingclient:billing:2.0.1'
+    androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    androidTestImplementation 'com.android.support.test:rules:1.0.2'
+    implementation 'com.android.support:support-annotations:28.0.0'
+    implementation 'com.android.billingclient:billing:2.0.1'
 }
 
 configurations.archives.extendsFrom configurations.default
@@ -126,8 +126,8 @@ android.libraryVariants.all { variant ->
         return; // Skip debug builds.
     }
     def task = project.tasks.create "jar${name.capitalize()}", Jar
-    task.dependsOn variant.javaCompile
-    task.from variant.javaCompile.destinationDir
+    task.dependsOn variant.javaCompileProvider
+    task.from variant.javaCompileProvider.get().destinationDir
     task.baseName 'anjlab-iabv3'
     task.doLast {
         println "Copying jar to sample project..."
diff --git a/sample/build.gradle b/sample/build.gradle
index b4d1a908..a4d3194d 100644
--- a/sample/build.gradle
+++ b/sample/build.gradle
@@ -1,19 +1,20 @@
 apply plugin: 'com.android.application'
 
 dependencies {
-    compile project(':library')
-//    compile fileTree(dir: 'libs', include: '*.jar')
+    implementation project(':library')
+//    implementation fileTree(dir: 'libs', include: '*.jar')
+    implementation 'com.android.support:support-annotations:28.0.0'
 }
 
 android {
-    compileSdkVersion 23
-    buildToolsVersion '25.0.3'
+    compileSdkVersion 26
+    buildToolsVersion '28.0.3'
 
     defaultConfig {
         versionCode 2
         versionName '1.0'
-        minSdkVersion 8
-        targetSdkVersion 23
+        minSdkVersion 9
+        targetSdkVersion 26
     }
 
     sourceSets.main {
diff --git a/sample/libs/anjlab-iabv3-current.jar b/sample/libs/anjlab-iabv3-current.jar
index 486f6f2e..f7d9d286 100644
Binary files a/sample/libs/anjlab-iabv3-current.jar and b/sample/libs/anjlab-iabv3-current.jar differ