diff --git a/src/cache-distributions/poetry-cache.ts b/src/cache-distributions/poetry-cache.ts
index ebbffbacf..c31fb05d4 100644
--- a/src/cache-distributions/poetry-cache.ts
+++ b/src/cache-distributions/poetry-cache.ts
@@ -46,7 +46,8 @@ class PoetryCache extends CacheDistributor {
 
   protected async computeKeys() {
     const hash = await glob.hashFiles(this.patterns);
-    const primaryKey = `${this.CACHE_KEY_PREFIX}-${process.env['RUNNER_OS']}-python-${this.pythonVersion}-${this.packageManager}-${hash}`;
+    // "v2" is here to invalidate old caches of this cache distributor, which were created broken:
+    const primaryKey = `${this.CACHE_KEY_PREFIX}-${process.env['RUNNER_OS']}-python-${this.pythonVersion}-${this.packageManager}-v2-${hash}`;
     const restoreKey = undefined;
     return {
       primaryKey,