diff --git a/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/AnnotationProcessorConstants.java b/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/AnnotationProcessorConstants.java
index a3ba59598..cf16510e6 100644
--- a/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/AnnotationProcessorConstants.java
+++ b/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/AnnotationProcessorConstants.java
@@ -1,3 +1,20 @@
+/*
+ * Copyright (C) 2018 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
 package com.velocitypowered.annotationprocessor;
 
 class AnnotationProcessorConstants {
diff --git a/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/ApiAnnotationProcessor.java b/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/ApiAnnotationProcessor.java
index add7dfdcf..0350d2974 100644
--- a/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/ApiAnnotationProcessor.java
+++ b/annotation-processor/src/main/java/com/velocitypowered/annotationprocessor/ApiAnnotationProcessor.java
@@ -88,7 +88,8 @@ public class ApiAnnotationProcessor extends AbstractProcessor {
           msg.printMessage(Diagnostic.Kind.ERROR,
               "method must not be abstract", method);
         }
-        if (method.getEnclosingElement().getKind().isInterface()) {
+        Element enclosing = method.getEnclosingElement();
+        if (enclosing != null && enclosing.getKind().isInterface()) {
           msg.printMessage(Diagnostic.Kind.ERROR,
               "interfaces cannot declare listeners", method);
         }
@@ -97,7 +98,8 @@ public class ApiAnnotationProcessor extends AbstractProcessor {
           msg.printMessage(Kind.ERROR, "method must return void or EventTask", method);
         }
         final List<? extends VariableElement> parameters = method.getParameters();
-        if (parameters.isEmpty() || !this.isTypeSubclass(parameters.get(0), SUBSCRIBE_ANNOTATION_CLASS)) {
+        if (parameters.isEmpty()
+            || !this.isTypeSubclass(parameters.get(0), SUBSCRIBE_ANNOTATION_CLASS)) {
           msg.printMessage(Diagnostic.Kind.ERROR,
               "method must have an Event as its first parameter", method);
         }
@@ -116,9 +118,9 @@ public class ApiAnnotationProcessor extends AbstractProcessor {
         if (Objects.equals(pluginClassFound, qualifiedName.toString())) {
           if (!warnedAboutMultiplePlugins) {
             processingEnv.getMessager()
-                .printMessage(Diagnostic.Kind.WARNING, "Velocity does not yet currently support "
-                    + "multiple plugins. We are using " + pluginClassFound
-                    + " for your plugin's main class.");
+                .printMessage(Diagnostic.Kind.WARNING,
+                    "Velocity does not yet currently support multiple plugins. "
+                        + "We are using " + pluginClassFound + " for your plugin's main class.");
             warnedAboutMultiplePlugins = true;
           }
           return false;
@@ -126,10 +128,10 @@ public class ApiAnnotationProcessor extends AbstractProcessor {
 
         Plugin plugin = element.getAnnotation(Plugin.class);
         if (!SerializedPluginDescription.ID_PATTERN.matcher(plugin.id()).matches()) {
-          processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR, "Invalid ID for plugin "
-              + qualifiedName
-              + ". IDs must start alphabetically, have alphanumeric characters, and can "
-              + "contain dashes or underscores.");
+          processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR,
+              "Invalid ID for plugin " + qualifiedName + ". "
+                  + "IDs must start alphabetically, have alphanumeric characters, and can "
+                  + "contain dashes or underscores.");
           return false;
         }
 
diff --git a/api/src/main/java/com/velocitypowered/api/event/Event.java b/api/src/main/java/com/velocitypowered/api/event/Event.java
index 4d0568f55..36b6b2420 100644
--- a/api/src/main/java/com/velocitypowered/api/event/Event.java
+++ b/api/src/main/java/com/velocitypowered/api/event/Event.java
@@ -1,3 +1,10 @@
+/*
+ * Copyright (C) 2018 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
 package com.velocitypowered.api.event;
 
 /**
diff --git a/proxy/src/test/java/com/velocitypowered/proxy/event/EventTest.java b/proxy/src/test/java/com/velocitypowered/proxy/event/EventTest.java
index cea6cc4da..8ec6f0f77 100644
--- a/proxy/src/test/java/com/velocitypowered/proxy/event/EventTest.java
+++ b/proxy/src/test/java/com/velocitypowered/proxy/event/EventTest.java
@@ -20,6 +20,7 @@ package com.velocitypowered.proxy.event;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import com.velocitypowered.api.event.Event;
 import com.velocitypowered.api.event.EventTask;
 import com.velocitypowered.api.event.PostOrder;
 import com.velocitypowered.api.event.Subscribe;
@@ -41,7 +42,7 @@ public class EventTest {
     eventManager.shutdown();
   }
 
-  static final class TestEvent {
+  static final class TestEvent implements Event {
   }
 
   static void assertAsyncThread(final Thread thread) {