diff --git a/biz.ganttproject.mxgraph/build.gradle b/biz.ganttproject.mxgraph/build.gradle
index d3765ef059..7cf3a91501 100644
--- a/biz.ganttproject.mxgraph/build.gradle
+++ b/biz.ganttproject.mxgraph/build.gradle
@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '2.0.20'
+    ext.kotlin_version = '2.0.21'
     repositories {
         mavenCentral()
     }
diff --git a/build.gradle b/build.gradle
index 2751edbe3c..0a6105841b 100644
--- a/build.gradle
+++ b/build.gradle
@@ -29,7 +29,7 @@ allprojects {
     ext {
         libDir = 'lib'
         mvnDir = 'lib/mvn'
-        kotlin_version = "2.0.20"
+        kotlin_version = "2.0.21"
         java_version = "21"
         javaExportOptions = [
             '--add-exports', 'javafx.controls/com.sun.javafx.scene.control.behavior=ALL-UNNAMED',
diff --git a/ganttproject-tester/build.gradle b/ganttproject-tester/build.gradle
index 7736c5904f..3398a9a9f8 100644
--- a/ganttproject-tester/build.gradle
+++ b/ganttproject-tester/build.gradle
@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '2.0.20'
+    ext.kotlin_version = '2.0.21'
     repositories {
         mavenCentral()
     }