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Co-authored-by: Antonio Muniz <[email protected]>

src/main/java/hudson/plugins/ec2/EC2Cloud.java

@@ -132,7 +132,7 @@ public abstract class EC2Cloud extends Cloud {
 
     // if this system property is defined and its value points to a valid ssh private key on disk
     // then this will be used instead of any configured ssh credential
-    private static final String sshPrivateKeyFilePath =EC2Cloud.class.getName() + "sshPrivateKeyFilePath";
+    private static final String SSH_PRIVATE_KEY_FILEPATH = EC2Cloud.class.getName() + ".sshPrivateKeyFilePath";
 
     private transient ReentrantLock slaveCountingLock = new ReentrantLock();
 
@@ -215,6 +215,7 @@ public EC2PrivateKey resolvePrivateKey(){
         return null;
     }
 
+    @CheckForNull
     private static EC2PrivateKey fetchPrivateKeyFromDisk()  {
         String filename = System.getProperty(sshPrivateKeyFilePath, "");
         if (!filename.isEmpty()) {