diff --git a/src/cmd/covdata/metamerge.go b/src/cmd/covdata/metamerge.go
index b3c62460e4..5193593456 100644
--- a/src/cmd/covdata/metamerge.go
+++ b/src/cmd/covdata/metamerge.go
@@ -241,6 +241,12 @@ func (mm *metaMerge) emitMeta(outdir string, pcombine bool) [16]byte {
 		fatal("unable to open output meta-data file %s: %v", fpath, err)
 	}
 
+	defer func() {
+		if err := mf.Close(); err != nil {
+			fatal("error closing output meta-data file %s: %v", fpath, err)
+		}
+	}()
+
 	// Encode and write.
 	mfw := encodemeta.NewCoverageMetaFileWriter(fpath, mf)
 	err = mfw.Write(finalHash, blobs, mm.Mode(), mm.Granularity())