diff --git a/wpe/src/main/java/com/wpe/wpe/WKCookieManager.java b/wpe/src/main/java/com/wpe/wpe/WKCookieManager.java
index 35b5e1ff3..3942bdf36 100644
--- a/wpe/src/main/java/com/wpe/wpe/WKCookieManager.java
+++ b/wpe/src/main/java/com/wpe/wpe/WKCookieManager.java
@@ -1,5 +1,7 @@
 package com.wpe.wpe;
 
+import androidx.annotation.NonNull;
+
 public class WKCookieManager {
     public enum CookieAcceptPolicy {
         AcceptAlways(0),
@@ -10,7 +12,7 @@ public enum CookieAcceptPolicy {
 
         CookieAcceptPolicy(int value) { this.value = value; }
 
-        private int getValue() { return value; }
+        int getValue() { return value; }
     }
 
     protected long nativePtr;
@@ -19,9 +21,9 @@ public enum CookieAcceptPolicy {
 
     WKCookieManager(long nativePtr) { this.nativePtr = nativePtr; }
 
-    public CookieAcceptPolicy getCookieAcceptPolicy() { return cookieAcceptPolicy; }
+    public @NonNull CookieAcceptPolicy getCookieAcceptPolicy() { return cookieAcceptPolicy; }
 
-    public void setCookieAcceptPolicy(CookieAcceptPolicy policy) {
+    public void setCookieAcceptPolicy(@NonNull CookieAcceptPolicy policy) {
         cookieAcceptPolicy = policy;
         nativeSetCookieAcceptPolicy(nativePtr, policy.getValue());
     }
diff --git a/wpe/src/main/java/com/wpe/wpe/WKWebContext.java b/wpe/src/main/java/com/wpe/wpe/WKWebContext.java
index 0e1ec0aed..42d339b7b 100644
--- a/wpe/src/main/java/com/wpe/wpe/WKWebContext.java
+++ b/wpe/src/main/java/com/wpe/wpe/WKWebContext.java
@@ -49,7 +49,7 @@ public void destroy() {
 
     public @NonNull WKWebsiteDataManager getWebsiteDataManager() { return websiteDataManager; }
 
-    public void setClient(Client client) { this.client = client; }
+    public void setClient(@Nullable Client client) { this.client = client; }
 
     @Keep
     private long createPageForAutomation() {
diff --git a/wpe/src/main/java/com/wpe/wpe/WKWebsiteDataManager.java b/wpe/src/main/java/com/wpe/wpe/WKWebsiteDataManager.java
index d329e15d8..5d843b65b 100644
--- a/wpe/src/main/java/com/wpe/wpe/WKWebsiteDataManager.java
+++ b/wpe/src/main/java/com/wpe/wpe/WKWebsiteDataManager.java
@@ -54,7 +54,7 @@ void destroy() {
         return cookieManager;
     }
 
-    public void clear(EnumSet<WebsiteDataType> websiteDataTypes, @Nullable Callback callback) {
+    public void clear(@NonNull EnumSet<WebsiteDataType> websiteDataTypes, @Nullable Callback callback) {
         int flags = websiteDataTypes.stream().map(WebsiteDataType::getValue).reduce(0, (x, y) -> x | y);
         if (flags != 0) {
             nativeClear(nativePtr, flags, new CallbackHolder(callback));
diff --git a/wpe/src/main/java/com/wpe/wpeview/WPEContext.java b/wpe/src/main/java/com/wpe/wpeview/WPEContext.java
index 5f72b5943..7bcad20a2 100644
--- a/wpe/src/main/java/com/wpe/wpeview/WPEContext.java
+++ b/wpe/src/main/java/com/wpe/wpeview/WPEContext.java
@@ -5,7 +5,6 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
-import com.wpe.wpe.Page;
 import com.wpe.wpe.WKWebContext;
 
 public class WPEContext {
@@ -35,7 +34,7 @@ public WPEContext(@NonNull Context context, boolean automationMode) {
         return cookieManager;
     }
 
-    public void setClient(WPEContext.Client client) {
+    public void setClient(@Nullable WPEContext.Client client) {
         this.client = client;
 
         if (client != null) {
diff --git a/wpe/src/main/java/com/wpe/wpeview/WPECookieManager.java b/wpe/src/main/java/com/wpe/wpeview/WPECookieManager.java
index 17b219495..79811805d 100644
--- a/wpe/src/main/java/com/wpe/wpeview/WPECookieManager.java
+++ b/wpe/src/main/java/com/wpe/wpeview/WPECookieManager.java
@@ -19,6 +19,7 @@
 
 package com.wpe.wpeview;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import com.wpe.wpe.WKCookieManager;
@@ -53,11 +54,11 @@ public interface Callback {
         this.cookieManager = dataManager.getCookieManager();
     }
 
-    public CookieAcceptPolicy getCookieAcceptPolicy() {
+    public @NonNull CookieAcceptPolicy getCookieAcceptPolicy() {
         return CookieAcceptPolicy.values()[cookieManager.getCookieAcceptPolicy().ordinal()];
     }
 
-    public void setCookieAcceptPolicy(CookieAcceptPolicy policy) {
+    public void setCookieAcceptPolicy(@NonNull CookieAcceptPolicy policy) {
         cookieManager.setCookieAcceptPolicy(WKCookieManager.CookieAcceptPolicy.values()[policy.ordinal()]);
     }