diff --git a/R/RPSS.R b/R/RPSS.R
index 5c7006c31ff155049d9c09ae09dfb123546acf7d..62730d9d5ad25f125ed66215a98cbd4f7b0e46b0 100644
--- a/R/RPSS.R
+++ b/R/RPSS.R
@@ -262,6 +262,22 @@ RPSS <- function(exp, obs, ref = NULL, time_dim = 'sdate', memb_dim = 'member',
         any(prob_thresholds <= 0) | any(prob_thresholds >= 1)) {
       stop("Parameter 'prob_thresholds' must be a numeric vector between 0 and 1.")
     }
+    if (missing(prob_thresholds)) {
+      if (is.null(cat_dim) && is.null(ref)) {
+        .warning("Parameter 'prob_thresholds' is not provided. Default value c(1/3, 2/3) is used.\n",
+                 "Since the inputs are ensemble members (i.e., 'cat_dim' is NULL) and no reference ",
+                 "forecast is provided, this default will be used both to compute category ",
+                 "probabilities and the reference climatology.")
+      } else if (is.null(cat_dim) && !is.null(ref)) {
+        .warning("Parameter 'prob_thresholds' is not provided. Default value c(1/3, 2/3) is used.\n",
+                 "Since the inputs are ensemble members (i.e., 'cat_dim' is NULL), this default will ",
+                 "be used to compute category probabilities.")
+      } else { # if (!is.null(cat_dim) && is.null(ref))
+        .warning("Parameter 'prob_thresholds' is not provided. Default value c(1/3, 2/3) is used.\n",
+                 "Since no reference forecast is provided, this default will be used to compute ",
+                 "the reference climatology.")
+      }
+    }
   }
   ## indices_for_clim
   if (is.null(indices_for_clim)) {