When deploying GAE I get "IllegalArgumentException: Class file is Java 8 but max supported is Java 7", but I'm using Java 7 everywhere
<p>I'm trying to deploy a Google App Engine project with the help of Eclipse Luna 4.4, but whenever I go to "Deploy to App Engine" I get the following error message:</p>

<blockquote>
  <p>------------ Deploying frontend ------------</p>
  
  <p>Preparing to deploy:  Created staging directory at:
  'C:\Users\ [[USERNAME]]~1\AppData\Local\Temp\appcfg6715651699721496450.tmp'
  java.lang.IllegalArgumentException: Class file is Java 8 but max
  supported is Java 7: C:\Users\ [[USERNAME]]\ ..HEALTH
  APP\Api\war\WEB-INF\classes\com\example\mycompany\myapplication\api\buses\BusEventSingleton.class</p>
  
  <p>Debugging information may be found in C:\Users\ [[USERNAME]]\AppData\Local\Temp\appengine-deploy4610763336673097422.log</p>
</blockquote>

<p>But in <strong>Project right click -> Properties</strong> I can see how the Java Compiler level is 1.7:</p>

<p><a href="https://i.stack.imgur.com/PEKpY.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PEKpY.jpg" alt="Java Compiler level is 1.7"></a></p>

<p>and how the Project Facets also establishes Java version as 1.7:</p>

<p><a href="https://i.stack.imgur.com/Y1J4I.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Y1J4I.jpg" alt="Java version as 1.7"></a></p>

<p>So anyone knows why I get this message? What is being compiled with Java 8 and how can I change it?</p>