diff --git a/task.js b/task.js
index a783df6a..4e8e9f5c 100644
--- a/task.js
+++ b/task.js
@@ -65,7 +65,7 @@ let coverageMap = (() => {
   return istanbul.createCoverageMap(previousCoverage)
 })()
 
-function saveCoverage(coverage) {
+function saveCoverage(coverage = coverageMap) {
   if (!existsSync(nycReportOptions.tempDir)) {
     mkdirSync(nycReportOptions.tempDir, { recursive: true })
     debug('created folder %s for output coverage', nycReportOptions.tempDir)