--- a/build.gradle
+++ b/build.gradle
@@ -45,17 +45,17 @@ buildscript {
             }
         }
         // For in tree plugins.
         maven {
             url "file://${gradle.mozconfig.topsrcdir}/mobile/android/gradle/m2repo"
         }
     }
 
-    ext.kotlin_version = '1.1.51'
+    ext.kotlin_version = '1.2.41'
     ext.support_library_version = '23.4.0'
 
     if (gradle.mozconfig.substs.MOZ_ANDROID_GOOGLE_PLAY_SERVICES) {
         ext.google_play_services_version = '8.4.0'
     }
 
     dependencies {
         classpath 'com.android.tools.build:gradle:3.0.1'

--- a/mobile/android/geckoview/build.gradle
+++ b/mobile/android/geckoview/build.gradle
@@ -169,16 +169,20 @@ tasks.withType(org.jetbrains.kotlin.grad
             }
             def (_, type, file, line, column, message) = matches[0]
             type = (type == 'w') ? 'warning' : 'error'
             // Use logger.lifecycle, which does not go through stderr again.
             logger.lifecycle "$file:$line:$column: $type: $message"
         }
     } as StandardOutputListener
 
+    kotlinOptions {
+        allWarningsAsErrors = true
+    }
+
     doFirst {
         logging.addStandardErrorListener(listener)
     }
     doLast {
         logging.removeStandardErrorListener(listener)
     }
 }