diff --git a/.travis.yml b/.travis.yml
index 3d0c36340..ff0d0f19d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,4 +7,5 @@ cache:
   - $HOME/.gradle/caches/
   - $HOME/.gradle/wrapper/
 jdk:
-  - openjdk8
\ No newline at end of file
+  - openjdk8
+  - openjdk11
\ No newline at end of file
diff --git a/api/build.gradle b/api/build.gradle
index a9e466865..edf3dc198 100644
--- a/api/build.gradle
+++ b/api/build.gradle
@@ -73,6 +73,9 @@ javadoc {
 
     // Disable the crazy super-strict doclint tool in Java 8
     options.addStringOption('Xdoclint:none', '-quiet')
+    
+    // Mark sources as Java 8 source compatible
+    options.source = '8'
 }
 
 publishing {