diff --git a/src/cache-base.ts b/src/cache-base.ts
index ce035642..e47b7a4e 100644
--- a/src/cache-base.ts
+++ b/src/cache-base.ts
@@ -204,15 +204,27 @@ export class GradleStateCache {
             fs.writeFileSync(initScriptPath, initScriptContent)
         }
 
-        // Copy the toolchain definitions file to `~/.m2/toolchains.xml` (if the file doesn't already exist)
+        // Copy the default toolchain definitions to `~/.m2/toolchains.xml`
+        const toolchainContent = this.readResourceFileAsString('toolchains.xml')
         const m2dir = path.resolve(this.userHome, '.m2')
         const toolchainXmlTarget = path.resolve(m2dir, 'toolchains.xml')
         if (!fs.existsSync(toolchainXmlTarget)) {
+            // Write a new toolchains.xml file if it doesn't exist
             fs.mkdirSync(m2dir, {recursive: true})
-            const toolchainContent = this.readResourceFileAsString('toolchains.xml')
             fs.writeFileSync(toolchainXmlTarget, toolchainContent)
 
             core.info(`Wrote default JDK locations to ${toolchainXmlTarget}`)
+        } else {
+            // Merge into an existing toolchains.xml file
+            const existingToolchainContent = fs.readFileSync(toolchainXmlTarget, 'utf8')
+            const appendedContent = toolchainContent.split("<toolchains>").pop()!
+            const mergedContent = existingToolchainContent.replace('</toolchains>', appendedContent)
+
+            core.info(`Merged toolchains.xml`)
+            core.info(mergedContent)
+
+            fs.writeFileSync(mergedContent, toolchainXmlTarget)
+            core.info(`Merged default JDK locations into ${toolchainXmlTarget}`)
         }
     }