Merge pull request #1135 from k163377/fix-1129

Set apiVersion and languageVersion to 1.9

Author: k163377

README.md

@@ -112,6 +112,7 @@ Different `kotlin-core` versions are supported by different Jackson Kotlin modul
 Here is an incomplete list of supported versions:
 
 * Jackson 2.21.x: Kotlin-core 2.1 - 2.3
+  * Starting with version 2.21.2, compatibility with Kotlin 1.9 is provided(see [#1129](https://github.com/FasterXML/jackson-module-kotlin/issues/1129)).
 * Jackson 2.20.x: Kotlin-core 2.0 - 2.2
 * Jackson 2.19.x: Kotlin-core 1.9 - 2.1
 

pom.xml

@@ -142,6 +142,11 @@
                 <artifactId>kotlin-maven-plugin</artifactId>
                 <groupId>org.jetbrains.kotlin</groupId>
                 <version>${version.kotlin}</version>
+                <!-- Based on discussion #1129, version 2.21 provides compatibility with Kotlin 1.9. -->
+                <configuration>
+                    <apiVersion>1.9</apiVersion>
+                    <languageVersion>1.9</languageVersion>
+                </configuration>
 
                 <executions>
                     <execution>

release-notes/CREDITS-2.x

@@ -15,6 +15,11 @@ Authors:
 
 Contributors:
 
+# 2.21.2 (not yet released)
+
+WrongWrong (@k163377)
+* #1135: Set apiVersion and languageVersion to 1.9
+
 # 2.21.0 (18-Jan-2026)
 
 WrongWrong (@k163377)

release-notes/VERSION-2.x

@@ -16,6 +16,10 @@ Co-maintainers:
 === Releases ===
 ------------------------------------------------------------------------
 
+2.21.2 (not yet released)
+
+#1135: Compatibility with Kotlin 1.9 is provided(see #1129).
+
 2.21.1 (22-Feb-2026)
 
 No changes since 2.21.0