diff --git a/DESCRIPTION b/DESCRIPTION
index bdd74e17453423fa80d336be9803424ad9d5549f..bcb3898d8db991761672cccc89ab9e9a972ea963 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: airGRteaching
 Type: Package
 Title: Tools to Simplify the Use of the airGR Hydrological Package for Education (Including a Shiny Interface)
-Version: 0.1.11.2
+Version: 0.1.11.3
 Date: 2018-01-29
 Authors@R: c(person("Olivier", "Delaigue", role = c("aut", "cre"), email = "airGR@irstea.fr"), person("Laurent", "Coron", role = c("aut")), person("Pierre", "Brigode", role = c("aut")), person("Guillaume", "Thirel", role = c("ctb")))
 Depends: airGR (>= 1.0.9.43)
diff --git a/R/CalGR.R b/R/CalGR.R
index dc549eaddc60c5fc2db3c7a8b4618c06bd537ba8..76507f8273cb53f225f9220faeda511000691762 100644
--- a/R/CalGR.R
+++ b/R/CalGR.R
@@ -8,6 +8,9 @@ CalGR <- function(PrepGR, CalCrit = c("NSE", "KGE", "KGE2", "RMSE"),
   WupInd <- NULL
   if (!is.null(WupPer)) {
     WupPer <- as.POSIXct(WupPer, tz = "UTC")
+    if (length(WupPer) != 2) {
+      stop("Warm-up period \"WupPer\" must be of length 2")
+    }
     if (any(is.na(WupPer))) {
       stop("Non convenient date format for the warm-up period \"WupPer\"")
     } else {
@@ -20,6 +23,9 @@ CalGR <- function(PrepGR, CalCrit = c("NSE", "KGE", "KGE2", "RMSE"),
   }
   
   CalPer <- as.POSIXct(CalPer, tz = "UTC")
+  if (length(CalPer) != 2) {
+    stop("Calibration period \"CalPer\" must be of length 2")
+  }
   if (any(is.na(CalPer))) {
     stop("Non convenient date format for the calibration period \"CalPer\"")
   } else {
diff --git a/R/SimGR.R b/R/SimGR.R
index 20812d53b8875458e46a6b9b8156c9e00ad3a6e7..e1e329e4543066aefc3c1c14afa9ece7d5580ec3 100644
--- a/R/SimGR.R
+++ b/R/SimGR.R
@@ -9,7 +9,7 @@ SimGR <- function(PrepGR, CalGR = NULL, Param = NULL, EffCrit = c("NSE", "KGE",
     stop("Non convenient data  for argument \"CalGR\". Must be of class \"CalGR\"")
   }
   if (is.null(CalGR) & is.null(Param)) {
-    stop("Arguments \"CalGR\" and \"Param\" are missing, with no default. You must fill in one of these two arguments.")
+    stop("Arguments \"CalGR\" and \"Param\" are missing, with no default. You must fill in one of these two arguments")
   }
   
   if (is.null(Param)) {
@@ -19,6 +19,9 @@ SimGR <- function(PrepGR, CalGR = NULL, Param = NULL, EffCrit = c("NSE", "KGE",
   WupInd <- NULL
   if (!is.null(WupPer)) {
     WupPer <- as.POSIXct(WupPer, tz = "UTC")
+    if (length(WupPer) != 2) {
+      stop("Warm-up period \"WupPer\" must be of length 2")
+    }
     if (any(is.na(WupPer))) {
       stop("Non convenient date format for the warm-up period \"WupPer\"")
     } else {
@@ -31,6 +34,9 @@ SimGR <- function(PrepGR, CalGR = NULL, Param = NULL, EffCrit = c("NSE", "KGE",
   }
  
   SimPer <- as.POSIXct(SimPer, tz = "UTC")
+  if (length(SimPer) != 2) {
+    stop("Simulation period \"SimPer\" must be of length 2")
+  }
   if (any(is.na(SimPer))) {
     stop("Non convenient date format for the simulation period \"SimPer\"")
   } else {