diff --git a/DESCRIPTION b/DESCRIPTION
index 3a14721e653cc44d481e8ee09e730f9aabee3ab1..3394a24178da497241f28fe833107d7cf295be9d 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: airGR
 Type: Package
 Title: Suite of GR Hydrological Models for Precipitation-Runoff Modelling
-Version: 1.4.4.20
+Version: 1.4.4.21
 Date: 2020-04-20
 Authors@R: c(
   person("Laurent", "Coron", role = c("aut", "trl"), comment = c(ORCID = "0000-0002-1503-6204")),
diff --git a/NEWS.md b/NEWS.md
index 883bfa59464ffe786b8e92f6d497b32015cc4a97..c115dedd3ca3b8df507449c55f6c70a9c60aad4a 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,7 +4,7 @@
 
 
 
-### 1.4.4.20 Release Notes (2020-04-20)
+### 1.4.4.21 Release Notes (2020-04-20)
 
 #### New features
 
diff --git a/R/SeriesAggreg2.R b/R/SeriesAggreg2.R
index 9e2a7aac9581c72d29684eadde4047d5bbc7c79b..d3745c7a4b1567ccdf5e4d74eb01203e4cba0644 100644
--- a/R/SeriesAggreg2.R
+++ b/R/SeriesAggreg2.R
@@ -7,6 +7,8 @@ SeriesAggreg2 <- function(TabSeries, Format, TimeFormat, NewTimeFormat, ConvertF
   }
   if (!missing(NewTimeFormat)) {
     if (missing(Format)) {
+      TimeStep <- c("hourly", "daily", "monthly", "yearly")
+      NewTimeFormat <- match.arg(NewTimeFormat, choices = TimeStep)
       Format <- switch(NewTimeFormat,
                        hourly  = "%Y%m%d%h",
                        daily   = "%Y%m%d",