diff --git a/samples/calculator/android/build.gradle b/samples/calculator/android/build.gradle
index 3c9cf238013..b97516566b9 100644
--- a/samples/calculator/android/build.gradle
+++ b/samples/calculator/android/build.gradle
@@ -8,7 +8,7 @@ buildscript {
 
     dependencies {
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath 'com.android.tools.build:gradle:3.1.3'
+        classpath 'com.android.tools.build:gradle:3.1.4'
     }
 }
 
@@ -24,6 +24,10 @@ android {
         versionCode 1
         versionName "1.0.0"
     }
+    sourceSets {
+      main.java.srcDirs += 'src/main/kotlin'
+      main.java.srcDirs += '../common/src/main/kotlin'
+    }
 }
 
 repositories {