diff --git a/ff4j-spring-rest-api/src/test/kotlin/org/ff4j/spring/rest/api/resources/ff4j/FF4JResourceStepDef.kt b/ff4j-spring-rest-api/src/test/kotlin/org/ff4j/spring/rest/api/resources/ff4j/FF4JResourceStepDef.kt
index f122376a..28009fb5 100644
--- a/ff4j-spring-rest-api/src/test/kotlin/org/ff4j/spring/rest/api/resources/ff4j/FF4JResourceStepDef.kt
+++ b/ff4j-spring-rest-api/src/test/kotlin/org/ff4j/spring/rest/api/resources/ff4j/FF4JResourceStepDef.kt
@@ -110,8 +110,8 @@ class FF4JResourceStepDef(ff4j: FF4j, context: WebApplicationContext) : En {
     uriBuilder: UriBuilder,
     path: String,
     formParams: Map<String, String>
-  ): URI? {
-    formParams.forEach { (name: String?, values: String?) ->
+  ): URI {
+    formParams.forEach { (name: String, values: String) ->
       uriBuilder.queryParam(
         name,
         values
diff --git a/ff4j-spring-rest-api/src/test/resources/features/FF4JResource.feature b/ff4j-spring-rest-api/src/test/resources/features/FF4JResource.feature
index e2afbcae..e60b27bf 100644
--- a/ff4j-spring-rest-api/src/test/resources/features/FF4JResource.feature
+++ b/ff4j-spring-rest-api/src/test/resources/features/FF4JResource.feature
@@ -60,7 +60,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "no security has been defined",
@@ -99,7 +98,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -166,7 +164,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -217,7 +214,6 @@ Feature:
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "bad request",
diff --git a/ff4j-spring-rest-api/src/test/resources/features/FeatureResource.feature b/ff4j-spring-rest-api/src/test/resources/features/FeatureResource.feature
index 91465772..b4b31d4d 100644
--- a/ff4j-spring-rest-api/src/test/resources/features/FeatureResource.feature
+++ b/ff4j-spring-rest-api/src/test/resources/features/FeatureResource.feature
@@ -20,7 +20,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -49,7 +48,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "feature uid cannot be blank",
@@ -69,7 +67,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "feature uid did not match with the requested feature uid to be created or updated",
@@ -186,7 +183,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "flipping strategy specified wrongly",
@@ -233,7 +229,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "properties specified wrongly",
@@ -265,7 +260,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -279,7 +273,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -312,7 +305,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -345,7 +337,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -360,7 +351,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -395,7 +385,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "304" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Modified",
       "status": 304,
       "detail": "role already exists",
@@ -421,7 +410,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -456,7 +444,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "role does not exist",
@@ -482,7 +469,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -498,7 +484,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "304" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Modified",
       "status": 304,
       "detail": "group already exists",
@@ -543,7 +528,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature not found",
@@ -578,7 +562,6 @@ Feature: FeatureResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "group does not exist",
diff --git a/ff4j-spring-rest-api/src/test/resources/features/FeatureStoreResource.feature b/ff4j-spring-rest-api/src/test/resources/features/FeatureStoreResource.feature
index d8664355..01e30887 100644
--- a/ff4j-spring-rest-api/src/test/resources/features/FeatureStoreResource.feature
+++ b/ff4j-spring-rest-api/src/test/resources/features/FeatureStoreResource.feature
@@ -133,7 +133,6 @@ Feature: FeatureStoreResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature store is not cached",
@@ -194,7 +193,6 @@ Feature: FeatureStoreResource
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "feature store is not cached",
diff --git a/ff4j-spring-rest-api/src/test/resources/features/GroupResource.feature b/ff4j-spring-rest-api/src/test/resources/features/GroupResource.feature
index c6369130..2f861d6d 100644
--- a/ff4j-spring-rest-api/src/test/resources/features/GroupResource.feature
+++ b/ff4j-spring-rest-api/src/test/resources/features/GroupResource.feature
@@ -51,7 +51,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
   """
   {
-    "type": "about:blank",
     "title": "Not Found",
     "status": 404,
     "detail": "group does not exist",
@@ -87,7 +86,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "group does not exist",
@@ -123,7 +121,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "group does not exist",
diff --git a/ff4j-spring-rest-api/src/test/resources/features/PropertyResource.feature b/ff4j-spring-rest-api/src/test/resources/features/PropertyResource.feature
index 14f1d640..d125eb71 100644
--- a/ff4j-spring-rest-api/src/test/resources/features/PropertyResource.feature
+++ b/ff4j-spring-rest-api/src/test/resources/features/PropertyResource.feature
@@ -34,7 +34,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "property not found",
@@ -81,7 +80,6 @@ Feature:
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "property name cannot be blank",
@@ -103,7 +101,6 @@ Feature:
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "property name did not match with the requested property name to be created or updated",
@@ -144,7 +141,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "property not found",
@@ -157,7 +153,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "property not found",
@@ -186,7 +181,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "property not found",
@@ -199,7 +193,6 @@ Feature:
     Then the user gets an error response with code "400" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Bad Request",
       "status": 400,
       "detail": "bad request",
diff --git a/ff4j-spring-rest-api/src/test/resources/features/PropertyStoreResource.feature b/ff4j-spring-rest-api/src/test/resources/features/PropertyStoreResource.feature
index bd58cf5e..3248fa25 100644
--- a/ff4j-spring-rest-api/src/test/resources/features/PropertyStoreResource.feature
+++ b/ff4j-spring-rest-api/src/test/resources/features/PropertyStoreResource.feature
@@ -92,7 +92,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "property store is not cached",
@@ -144,7 +143,6 @@ Feature:
     Then the user gets an error response with code "404" and error message as
     """
     {
-      "type": "about:blank",
       "title": "Not Found",
       "status": 404,
       "detail": "property store is not cached",
diff --git a/pom.xml b/pom.xml
index 7a538aa7..5532122e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -73,7 +73,7 @@
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <java.version>21</java.version>
-    <spring-boot.version>3.5.7</spring-boot.version>
+    <spring-boot.version>4.0.0</spring-boot.version>
     <ff4j.version>2.1</ff4j.version>
     <jackson-module-kotlin.version>2.20.1</jackson-module-kotlin.version>
     <kotlin.version>2.2.21</kotlin.version>