diff --git a/NEWS.md b/NEWS.md
index 090aa077eb00ecdba2613f6f86737519d78ba59a..d21702a5ff08aeada6a6eabd59286057eaef1c67 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -6,6 +6,7 @@
     + PlotForecastPDF vignette displays figures correctly
     + Calibration function is exposed to users
     + MultiMetric vignette fixed typo text description
+    + RainFARM checks 'slope' is not a vector
 
 
 ### CSTools 3.0.0
diff --git a/R/CST_RainFARM.R b/R/CST_RainFARM.R
index ff4d624dc7fa6f8f12f4183332bd4b79ba89f601..49065a974711aa9732778ee46e8ca9717ee667b9 100644
--- a/R/CST_RainFARM.R
+++ b/R/CST_RainFARM.R
@@ -237,6 +237,12 @@ RainFARM <- function(data, lon, lat, nf, weights = 1., nens = 1,
     }
     warning(paste("Selected time dim:", time_dim))
   }
+  # Check if slope is an array
+  if (length(slope) > 1) {
+    warning("Parameter 'slope' has length > 1 and only the first ",
+            "element will be used.")
+    slope <- as.numeric(slope[1])
+  }
 
   # Perform common calls
   r <- lon_lat_fine(lon, lat, nf)