diff --git a/R/RPSS.R b/R/RPSS.R
index 76c0dba37b5267017829a1ab9a8aa8bd80897758..5c7006c31ff155049d9c09ae09dfb123546acf7d 100644
--- a/R/RPSS.R
+++ b/R/RPSS.R
@@ -50,7 +50,12 @@
 #'  The default value is NULL.
 #'@param prob_thresholds A numeric vector of the relative thresholds (from 0 to
 #'  1) between the categories. The default value is c(1/3, 2/3), which 
-#'  corresponds to tercile equiprobable categories.
+#'  corresponds to tercile equiprobable categories. When the inputs are 
+#'  ensemble members ('cat_dim' is NULL), these thresholds are used to compute 
+#'  category probabilities. If 'ref' is NULL, the thresholds are also used to 
+#'  compute the reference forecast ('clim_probs'), even when 'exp' and 'obs' are 
+#'  already given as probabilities. If 'ref' is provided and the inputs are 
+#'  probabilities, 'prob_thresholds' is ignored.
 #'@param indices_for_clim A vector of the indices to be taken along 'time_dim' 
 #'  for computing the thresholds between the probabilistic categories. If NULL,
 #'  the whole period is used. The default value is NULL.
@@ -252,9 +257,11 @@ RPSS <- function(exp, obs, ref = NULL, time_dim = 'sdate', memb_dim = 'member',
     }
   }
   ## prob_thresholds
-  if (!is.numeric(prob_thresholds) | !is.vector(prob_thresholds) |
-      any(prob_thresholds <= 0) | any(prob_thresholds >= 1)) {
-    stop("Parameter 'prob_thresholds' must be a numeric vector between 0 and 1.")
+  if (is.null(cat_dim) || (!is.null(cat_dim) && is.null(ref))) {
+    if (!is.numeric(prob_thresholds) | !is.vector(prob_thresholds) |
+        any(prob_thresholds <= 0) | any(prob_thresholds >= 1)) {
+      stop("Parameter 'prob_thresholds' must be a numeric vector between 0 and 1.")
+    }
   }
   ## indices_for_clim
   if (is.null(indices_for_clim)) {