diff --git a/__tests__/cache-restore.test.ts b/__tests__/cache-restore.test.ts
index 44b400eef..d6ed8320b 100644
--- a/__tests__/cache-restore.test.ts
+++ b/__tests__/cache-restore.test.ts
@@ -183,6 +183,10 @@ virtualenvs.path = "{cache-dir}/virtualenvs"  # /Users/patrick/Library/Caches/py
           expect(infoSpy).toHaveBeenCalledWith(
             `Cache restored from key: setup-python-${process.env['RUNNER_OS']}-20.04-Ubuntu-python-${pythonVersion}-${packageManager}-${fileHash}`
           );
+        } else if (packageManager === 'poetry') {
+          expect(infoSpy).toHaveBeenCalledWith(
+            `Cache restored from key: setup-python-${process.env['RUNNER_OS']}-python-${pythonVersion}-${packageManager}-v2-${fileHash}`
+          );
         } else {
           expect(infoSpy).toHaveBeenCalledWith(
             `Cache restored from key: setup-python-${process.env['RUNNER_OS']}-python-${pythonVersion}-${packageManager}-${fileHash}`
diff --git a/dist/setup/index.js b/dist/setup/index.js
index 41ed58a1f..266dce5f4 100644
--- a/dist/setup/index.js
+++ b/dist/setup/index.js
@@ -66141,7 +66141,8 @@ class PoetryCache extends cache_distributor_1.default {
     computeKeys() {
         return __awaiter(this, void 0, void 0, function* () {
             const hash = yield 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,
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,