diff --git a/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationFilter.java b/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationFilter.java
index 6c82f9c9ef..aa4badcfb0 100644
--- a/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationFilter.java
+++ b/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationFilter.java
@@ -1,5 +1,6 @@
 package com.baeldung.apikeyauthentication.configuration;
 
+import org.springframework.http.MediaType;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.context.SecurityContextHolder;
 import org.springframework.web.filter.GenericFilterBean;
@@ -8,15 +9,28 @@ import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
+import java.io.PrintWriter;
 
 public class AuthenticationFilter extends GenericFilterBean {
 
     @Override
     public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
       throws IOException, ServletException {
-        Authentication authentication = AuthenticationService.getAuthentication((HttpServletRequest) request);
-        SecurityContextHolder.getContext().setAuthentication(authentication);
+        try {
+            Authentication authentication = AuthenticationService.getAuthentication((HttpServletRequest) request);
+            SecurityContextHolder.getContext().setAuthentication(authentication);
+        } catch (Exception exp) {
+            HttpServletResponse httpResponse = (HttpServletResponse) response;
+            httpResponse.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
+            httpResponse.setContentType(MediaType.APPLICATION_JSON_VALUE);
+            PrintWriter writer = httpResponse.getWriter();
+            writer.print(exp.getMessage());
+            writer.flush();
+            writer.close();
+        }
+
         filterChain.doFilter(request, response);
     }
 }
diff --git a/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationService.java b/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationService.java
index 14183f9f62..c788f7cdd8 100644
--- a/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationService.java
+++ b/spring-security-modules/spring-security-web-boot-4/src/main/java/com/baeldung/apikeyauthentication/configuration/AuthenticationService.java
@@ -1,5 +1,6 @@
 package com.baeldung.apikeyauthentication.configuration;
 
+import org.springframework.security.authentication.BadCredentialsException;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.authority.AuthorityUtils;
 import javax.servlet.http.HttpServletRequest;
@@ -11,10 +12,10 @@ public class AuthenticationService {
 
     public static Authentication getAuthentication(HttpServletRequest request) {
         String apiKey = request.getHeader(AUTH_TOKEN_HEADER_NAME);
-        if (apiKey != null && apiKey.equals(AUTH_TOKEN)) {
-            return new ApiKeyAuthentication(apiKey, AuthorityUtils.NO_AUTHORITIES);
+        if (apiKey == null || !apiKey.equals(AUTH_TOKEN)) {
+            throw new BadCredentialsException("Invalid API Key");
         }
 
-        return null;
+        return new ApiKeyAuthentication(apiKey, AuthorityUtils.NO_AUTHORITIES);
     }
 }