diff --git a/src/main/java/me/clip/placeholderapi/PlaceholderListener.java b/src/main/java/me/clip/placeholderapi/PlaceholderListener.java
index 04cc1fbe..050f02ce 100644
--- a/src/main/java/me/clip/placeholderapi/PlaceholderListener.java
+++ b/src/main/java/me/clip/placeholderapi/PlaceholderListener.java
@@ -40,7 +40,7 @@
 
 public class PlaceholderListener implements Listener {
 
-  private PlaceholderAPIPlugin plugin;
+  private final PlaceholderAPIPlugin plugin;
 
   public PlaceholderListener(PlaceholderAPIPlugin instance) {
     plugin = instance;
diff --git a/src/main/java/me/clip/placeholderapi/ServerLoadEventListener.java b/src/main/java/me/clip/placeholderapi/ServerLoadEventListener.java
index 71a9c5ce..855cd921 100644
--- a/src/main/java/me/clip/placeholderapi/ServerLoadEventListener.java
+++ b/src/main/java/me/clip/placeholderapi/ServerLoadEventListener.java
@@ -9,7 +9,7 @@
 
 public class ServerLoadEventListener implements Listener {
 
-    private PlaceholderAPIPlugin plugin;
+    private final PlaceholderAPIPlugin plugin;
 
     public ServerLoadEventListener(PlaceholderAPIPlugin instance) {
         plugin = instance;
diff --git a/src/main/java/me/clip/placeholderapi/commands/PlaceholderAPICommands.java b/src/main/java/me/clip/placeholderapi/commands/PlaceholderAPICommands.java
index 7ddf45ab..969e98fe 100644
--- a/src/main/java/me/clip/placeholderapi/commands/PlaceholderAPICommands.java
+++ b/src/main/java/me/clip/placeholderapi/commands/PlaceholderAPICommands.java
@@ -36,8 +36,8 @@
 
 public class PlaceholderAPICommands implements CommandExecutor {
 
-  private PlaceholderAPIPlugin plugin;
-  private CommandExecutor eCloud;
+  private final PlaceholderAPIPlugin plugin;
+  private final CommandExecutor eCloud;
 
   public PlaceholderAPICommands(PlaceholderAPIPlugin i) {
     plugin = i;
diff --git a/src/main/java/me/clip/placeholderapi/configuration/PlaceholderAPIConfig.java b/src/main/java/me/clip/placeholderapi/configuration/PlaceholderAPIConfig.java
index a8cdd8dd..8a27475c 100644
--- a/src/main/java/me/clip/placeholderapi/configuration/PlaceholderAPIConfig.java
+++ b/src/main/java/me/clip/placeholderapi/configuration/PlaceholderAPIConfig.java
@@ -24,7 +24,7 @@
 
 public class PlaceholderAPIConfig {
 
-  private PlaceholderAPIPlugin plugin;
+  private final PlaceholderAPIPlugin plugin;
 
   public PlaceholderAPIConfig(PlaceholderAPIPlugin i) {
     plugin = i;
diff --git a/src/main/java/me/clip/placeholderapi/events/ExpansionRegisterEvent.java b/src/main/java/me/clip/placeholderapi/events/ExpansionRegisterEvent.java
index fc78a667..4e1ba54a 100644
--- a/src/main/java/me/clip/placeholderapi/events/ExpansionRegisterEvent.java
+++ b/src/main/java/me/clip/placeholderapi/events/ExpansionRegisterEvent.java
@@ -27,7 +27,7 @@
 public class ExpansionRegisterEvent extends Event {
 
   private static final HandlerList HANDLERS = new HandlerList();
-  private PlaceholderExpansion expansion;
+  private final PlaceholderExpansion expansion;
 
   public ExpansionRegisterEvent(PlaceholderExpansion expansion) {
     this.expansion = expansion;
diff --git a/src/main/java/me/clip/placeholderapi/events/ExpansionUnregisterEvent.java b/src/main/java/me/clip/placeholderapi/events/ExpansionUnregisterEvent.java
index e5ba621c..405f1bb3 100644
--- a/src/main/java/me/clip/placeholderapi/events/ExpansionUnregisterEvent.java
+++ b/src/main/java/me/clip/placeholderapi/events/ExpansionUnregisterEvent.java
@@ -27,7 +27,7 @@
 public class ExpansionUnregisterEvent extends Event {
 
   private static final HandlerList HANDLERS = new HandlerList();
-  private PlaceholderExpansion expansion;
+  private final PlaceholderExpansion expansion;
 
   public ExpansionUnregisterEvent(PlaceholderExpansion expansion) {
     this.expansion = expansion;
diff --git a/src/main/java/me/clip/placeholderapi/events/PlaceholderHookUnloadEvent.java b/src/main/java/me/clip/placeholderapi/events/PlaceholderHookUnloadEvent.java
index 69ad53de..fb3d0cd3 100644
--- a/src/main/java/me/clip/placeholderapi/events/PlaceholderHookUnloadEvent.java
+++ b/src/main/java/me/clip/placeholderapi/events/PlaceholderHookUnloadEvent.java
@@ -28,8 +28,8 @@
 public class PlaceholderHookUnloadEvent extends Event {
 
   private static final HandlerList HANDLERS = new HandlerList();
-  private String plugin;
-  private PlaceholderHook hook;
+  private final String plugin;
+  private final PlaceholderHook hook;
 
   public PlaceholderHookUnloadEvent(String plugin, PlaceholderHook placeholderHook) {
     this.plugin = plugin;
diff --git a/src/main/java/me/clip/placeholderapi/expansion/ExpansionManager.java b/src/main/java/me/clip/placeholderapi/expansion/ExpansionManager.java
index e1499a46..1915dfab 100644
--- a/src/main/java/me/clip/placeholderapi/expansion/ExpansionManager.java
+++ b/src/main/java/me/clip/placeholderapi/expansion/ExpansionManager.java
@@ -36,7 +36,7 @@
 import java.util.Map.Entry;
 
 public final class ExpansionManager {
-  private PlaceholderAPIPlugin plugin;
+  private final PlaceholderAPIPlugin plugin;
 
   public ExpansionManager(PlaceholderAPIPlugin instance) {
     plugin = instance;
diff --git a/src/main/java/me/clip/placeholderapi/expansion/NMSVersion.java b/src/main/java/me/clip/placeholderapi/expansion/NMSVersion.java
index 21d6856b..1e739e2a 100644
--- a/src/main/java/me/clip/placeholderapi/expansion/NMSVersion.java
+++ b/src/main/java/me/clip/placeholderapi/expansion/NMSVersion.java
@@ -39,7 +39,7 @@ public enum NMSVersion {
   SPIGOT_1_13_R2("v1_13_R2"),
   SPIGOT_1_14_R1("v1_14_R1");
 
-  private String version;
+  private final String version;
 
   NMSVersion(String version) {
     this.version = version;
diff --git a/src/main/java/me/clip/placeholderapi/expansion/Version.java b/src/main/java/me/clip/placeholderapi/expansion/Version.java
index 3b046764..f8c0dbff 100644
--- a/src/main/java/me/clip/placeholderapi/expansion/Version.java
+++ b/src/main/java/me/clip/placeholderapi/expansion/Version.java
@@ -22,9 +22,8 @@
 
 public final class Version {
 
-  private boolean isSpigot;
-
-  private String version;
+  private final boolean isSpigot;
+  private final String version;
 
   public Version(String version, boolean isSpigot) {
     this.version = version;
diff --git a/src/main/java/me/clip/placeholderapi/external/EZPlaceholderHook.java b/src/main/java/me/clip/placeholderapi/external/EZPlaceholderHook.java
index 097e13e9..d22891f8 100644
--- a/src/main/java/me/clip/placeholderapi/external/EZPlaceholderHook.java
+++ b/src/main/java/me/clip/placeholderapi/external/EZPlaceholderHook.java
@@ -28,9 +28,8 @@
 @Deprecated
 public abstract class EZPlaceholderHook extends PlaceholderHook {
 
-  private String identifier;
-
-  private String plugin;
+  private final String identifier;
+  private final String plugin;
 
   public EZPlaceholderHook(Plugin plugin, String identifier) {
     Validate.notNull(plugin, "Plugin can not be null!");
diff --git a/src/main/java/me/clip/placeholderapi/updatechecker/UpdateChecker.java b/src/main/java/me/clip/placeholderapi/updatechecker/UpdateChecker.java
index 0325bb7f..04fdfddd 100644
--- a/src/main/java/me/clip/placeholderapi/updatechecker/UpdateChecker.java
+++ b/src/main/java/me/clip/placeholderapi/updatechecker/UpdateChecker.java
@@ -15,8 +15,9 @@
 public class UpdateChecker implements Listener {
 
   private final int RESOURCE_ID = 6245;
-  private PlaceholderAPIPlugin plugin;
-  private String spigotVersion, pluginVersion;
+  private final PlaceholderAPIPlugin plugin;
+  private String spigotVersion;
+  private final String pluginVersion;
   private boolean updateAvailable;
 
   public UpdateChecker(PlaceholderAPIPlugin i) {