diff --git a/lib/index.js b/lib/index.js
index 9e77a580..1b831216 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -142,7 +142,7 @@ class CoverageReport {
         }
 
         // GC, no OOM
-        this.fileCache = [];
+        this.fileCache.clear();
 
         const { dataList, sourceCache } = inputData;