diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 44388f2f..9d6e905d 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -16,7 +16,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 21
+          java-version: 17
           distribution: 'temurin'
       - name: Cache Gradle packages
         uses: actions/cache@v4
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b562299f..51ecf748 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -18,7 +18,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v3
         with:
-          java-version: 21
+          java-version: 17
           distribution: 'temurin'
       - name: Cache SonarCloud packages
         uses: actions/cache@v3
diff --git a/build.gradle.kts b/build.gradle.kts
index 58b11357..3a7412bb 100755
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -17,7 +17,7 @@ plugins {
     jacoco
     java
     kotlin("jvm") version "2.2.21" apply false
-    id("org.springframework.boot") version "4.0.1"
+    id("org.springframework.boot") version "4.0.5"
 }
 
 repositories {
@@ -62,7 +62,7 @@ allprojects {
         apply(plugin = "org.jmailen.kotlinter")
 
         java {
-            toolchain.languageVersion.set(JavaLanguageVersion.of(21))
+            toolchain.languageVersion.set(JavaLanguageVersion.of(17))
         }
     }
 }
@@ -72,7 +72,7 @@ subprojects {
     val jmustacheVersion by extra { "1.16" }
 
     tasks.withType<KotlinCompile> {
-        compilerOptions.jvmTarget.set(JvmTarget.JVM_21)
+        compilerOptions.jvmTarget.set(JvmTarget.JVM_17)
     }
 
     tasks.withType<Test> {
@@ -93,8 +93,8 @@ subprojects {
         }
 
         tasks.withType<JavaCompile> {
-            targetCompatibility = "21"
-            sourceCompatibility = "21"
+            targetCompatibility = "17"
+            sourceCompatibility = "17"
         }
     }
 }
diff --git a/gradle/gradle-daemon-jvm.properties b/gradle/gradle-daemon-jvm.properties
index 63e5bbdf..858feb7e 100644
--- a/gradle/gradle-daemon-jvm.properties
+++ b/gradle/gradle-daemon-jvm.properties
@@ -1,2 +1,2 @@
 #This file is generated by updateDaemonJvm
-toolchainVersion=21
+toolchainVersion=17
diff --git a/samples/restdocs-api-spec-sample-web-test-client/build.gradle b/samples/restdocs-api-spec-sample-web-test-client/build.gradle
index e18e1570..90f3a184 100644
--- a/samples/restdocs-api-spec-sample-web-test-client/build.gradle
+++ b/samples/restdocs-api-spec-sample-web-test-client/build.gradle
@@ -23,7 +23,7 @@ repositories {
 
 java {
     toolchain {
-        languageVersion = JavaLanguageVersion.of(21)
+        languageVersion = JavaLanguageVersion.of(17)
     }
 }
 
diff --git a/samples/restdocs-api-spec-sample/build.gradle b/samples/restdocs-api-spec-sample/build.gradle
index 7520e633..f94cb17e 100755
--- a/samples/restdocs-api-spec-sample/build.gradle
+++ b/samples/restdocs-api-spec-sample/build.gradle
@@ -20,7 +20,7 @@ apply plugin: 'com.epages.restdocs-api-spec'
 
 java {
     toolchain {
-        languageVersion = JavaLanguageVersion.of(21)
+        languageVersion = JavaLanguageVersion.of(17)
     }
 }