diff --git a/DESCRIPTION b/DESCRIPTION
index 3258fcf3663792f1946f6e736f5e3ae2b6ef47b7..b6e3ebabd45226a3779b589430bf8ddc2be018f2 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: airGR
 Type: Package
 Title: Suite of GR Hydrological Models for Precipitation-Runoff Modelling
-Version: 1.6.1.2
+Version: 1.6.1.3
 Date: 2020-04-05
 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 5517de7a88401d5a596307207fcfae187f319f9d..2c45deeba582015543c85e6ccc0d18280fc81e1c 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,7 +4,7 @@
 
 
 
-### 1.6.1.2 Release Notes (2020-04-05)
+### 1.6.1.3 Release Notes (2020-04-05)
 
 #### New features
 
diff --git a/R/RunModel.R b/R/RunModel.R
index 4fab1150b6b8619c125e3255735dd0b4103903af..a5d5824e5d81508bde0f4bd89f38bd90951a4eb7 100644
--- a/R/RunModel.R
+++ b/R/RunModel.R
@@ -1,18 +1,18 @@
 RunModel <- function (InputsModel, RunOptions, Param, FUN_MOD) {
   FUN_MOD <- match.fun(FUN_MOD)
-  if ("SD" %in% class(InputsModel)) {
+  if (inherits(InputsModel, "SD")) {
     Outputs_down <- FUN_MOD(InputsModel = InputsModel, RunOptions = RunOptions, 
                             Param = Param[-length(Param)])
     Outputs_down$Qdown <- Outputs_down$Qsim
-    if ("daily" %in% class(InputsModel)) {
+    if (inherits(InputsModel, "daily")) {
       TimeStep <- 60 * 60 * 24
     }
-    if ("hourly" %in% class(InputsModel)) {
+    if (inherits(InputsModel, "hourly")) {
       TimeStep <- 60 * 60
     }
     surf_tot <- sum(InputsModel$BasinAreas)
     Outputs_down$Qsim <- Outputs_down$Qdown * InputsModel$BasinAreas[length(InputsModel$BasinAreas)] / surf_tot +
-      1000 / tail(Param, 1) / TimeStep * 
+      1000 / Param[-length(Param)] / TimeStep * 
       InputsModel$QobsUpstr %*% (InputsModel$LengthHydro[1, ] * InputsModel$BasinAreas[1:length(InputsModel$LengthHydro)])
   } else {
     Outputs_down <- FUN_MOD(InputsModel = InputsModel, RunOptions = RunOptions, Param = Param)