diff --git a/DESCRIPTION b/DESCRIPTION
index 5ab57cb951bff4f61efa734e9855f6d83d66f75c..02d20cc45813594d00e99efbfc4b13608aa7e1c2 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: airGR
 Type: Package
 Title: Suite of GR Hydrological Models for Precipitation-Runoff Modelling
-Version: 1.4.4.14
+Version: 1.4.4.15
 Date: 2020-04-09
 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 d7a4baa116b1a73d2e60064c28dad9d6bfbf864d..83d0ca96bbba8e80f0aa130b2c8bd7b8d00e6c8c 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,7 +4,7 @@
 
 
 
-### 1.4.4.14 Release Notes (2020-04-09)
+### 1.4.4.15 Release Notes (2020-04-09)
 
 #### New features
 
diff --git a/R/SeriesAggreg2.R b/R/SeriesAggreg2.R
index befb899c6536f65e602c34665dca5c81fabcbbb4..6fbbffe6840fb3fde0cecdf285b0878ce075212b 100644
--- a/R/SeriesAggreg2.R
+++ b/R/SeriesAggreg2.R
@@ -28,20 +28,16 @@ SeriesAggreg2 <- function(TabSeries, Format, ConvertFun,
   Format <- gsub(pattern = "[[:punct:]]+", replacement = "%", Format)
   Format <- match.arg(Format, choices = listFormat)
   ## check ConvertFun
-  if (!is.vector(ConvertFun)) {
-    stop("'ConvertFun' must be a vector of character")
-  }
-  if (!is.character(ConvertFun)) {
-    stop("'ConvertFun' must be a vector of character")
+  listConvertFun <- c("sum", "mean")
+  ConvertFun <- listConvertFun[match(ConvertFun, listConvertFun)]
+  if (anyNA(ConvertFun)) {
+    stop("'ConvertFun' should be a one of 'sum' or 'mean'")
   }
   if (length(ConvertFun) != (ncol(TabSeries) - 1)) {
     stop(
       sprintf("'ConvertFun' must be of length %i (ncol(TabSeries)-1)", ncol(TabSeries) - 1)
     )
   }
-  if (!all(ConvertFun %in% c("sum", "mean"))) {
-    stop("'ConvertFun' should be one of 'sum' or 'mean'")
-  }
   ## check YearFirstMonth
   msgYearFirstMonth <- "'YearFirstMonth' should be a numeric value between 1 and 12"
   YearFirstMonth <- match(YearFirstMonth, 1:12)