diff --git a/crypto/key_store_plain.go b/crypto/key_store_plain.go
index 428d01e25..8c405ebcd 100644
--- a/crypto/key_store_plain.go
+++ b/crypto/key_store_plain.go
@@ -189,7 +189,7 @@ func toISO8601(t time.Time) string {
 	} else {
 		tz = fmt.Sprintf("%03d00", offset/3600)
 	}
-	return fmt.Sprintf("%04d-%02d-%02dT%02d:%02d:%02d.%09d%s", t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), tz)
+	return fmt.Sprintf("%04d-%02d-%02dT%02d-%02d-%02d.%09d%s", t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), tz)
 }
 
 func getKeyAddresses(keysDirPath string) (addresses []common.Address, err error) {