diff --git a/src/config.ts b/src/config.ts
index 15ca1cf..2c4897a 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -71,6 +71,10 @@ export class CacheConfig {
       }
     }
 
+    // Add runner OS to the key to avoid cross-contamination of cache
+    const runnerOS = os.type();
+    key += `-${runnerOS}`;
+
     self.keyPrefix = key;
 
     // Construct environment portion of the key: