diff --git a/R/prj_medium.R b/R/prj_medium.R
index 39eb2c9c0395f96266b422276e006ba4c0ffbe81..d216c0155f40722ebf7f040780b616d2c4b99dc9 100644
--- a/R/prj_medium.R
+++ b/R/prj_medium.R
@@ -13,6 +13,10 @@ r2ogs6_medium <- function(phases = NULL,
                           properties = NULL,
                           id = NULL) {
 
+    if(is.character(phases)){
+        phases <- NULL
+    }
+
     new_r2ogs6_medium(phases,
                       properties,
                       id)
diff --git a/R/prj_porous_medium.R b/R/prj_porous_medium.R
index d0a822903f73d9353a012e2fd79bd772ce408949..d23a6d7817fba2ecaf9755b0a5bc38451c761601 100644
--- a/R/prj_porous_medium.R
+++ b/R/prj_porous_medium.R
@@ -172,12 +172,12 @@ new_r2ogs6_capillary_pressure <- function(type,
 
 #'r2ogs6_relative_permeability
 #'@description tag: relative_permeability
-#'@param id
-#'@param type
-#'@param sr
-#'@param smax
-#'@param m
-#'@param krel_min
+#'@param type string:
+#'@param sr string | number:
+#'@param smax string | number:
+#'@param m string | number:
+#'@param krel_min string | number:
+#'@param id string: Optional:
 r2ogs6_relative_permeability <- function(type,
                                          sr,
                                          smax,
@@ -187,6 +187,11 @@ r2ogs6_relative_permeability <- function(type,
 
     # Add coercing utility here
 
+    sr <- coerce_string_to_numeric(sr)
+    smax <- coerce_string_to_numeric(smax)
+    m <- coerce_string_to_numeric(m)
+    krel_min <- coerce_string_to_numeric(krel_min)
+
     new_r2ogs6_relative_permeability(type,
                                      sr,
                                      smax,
@@ -202,6 +207,14 @@ new_r2ogs6_relative_permeability <- function(type,
                                              m,
                                              krel_min,
                                              id = NULL) {
+    validate_is_string(type)
+    validate_is_null_or_string(id)
+
+    validate_is_number(sr,
+                       smax,
+                       m,
+                       krel_min)
+
     structure(list(type = type,
                    sr = sr,
                    smax = smax,