diff --git a/R/Design.R b/R/Design.R
index ec4a7854..8070d6cf 100644
--- a/R/Design.R
+++ b/R/Design.R
@@ -109,7 +109,7 @@ Design = R6Class("Design",
           pcol = self$data[[dd$on[j]]]
           # we are ok if parent was active and cond on parent is OK
           not_ok = which(is.na(pcol) | !dd$cond[[j]]$test(pcol))
-          set(self$data, not_ok, j = param_id, value = as(NA, param$storage_type))
+          set(self$data, not_ok, j = param_id, value = as_type(NA, param$storage_type))
         }
       }
     }
diff --git a/R/Sampler1D.R b/R/Sampler1D.R
index 3e51de1f..c45d2661 100644
--- a/R/Sampler1D.R
+++ b/R/Sampler1D.R
@@ -30,7 +30,7 @@ Sampler1D = R6Class("Sampler1D", inherit = Sampler, # abstract base class
   private = list(
     # create a 1-col-dt, named by param-id, from a data vector (from sampling), and enforce storage type
     as_dt_col = function(x) {
-      x = get(sprintf("as.%s", self$param$storage_type), mode = "function", envir = baseenv())(x)
+      x = as_type(x, self$param$storage_type)
       set_names(data.table(x), self$param$id)
     }
   )
diff --git a/R/helper.R b/R/helper.R
index 9080921e..1585a1de 100644
--- a/R/helper.R
+++ b/R/helper.R
@@ -30,3 +30,13 @@ transpose = function(data, ps = NULL, filter_na = TRUE, trafo = TRUE) {
   }
   return(xs)
 }
+
+as_type = function(x, type) {
+  switch(type,
+    logical = as.logical(x),
+    integer = as.integer(x),
+    numeric = as.numeric(x),
+    character = as.character(x),
+    stopf("Invalid storage type '%s'", type)
+  )
+}
diff --git a/README.md b/README.md
index dcadb6aa..5d91c6ba 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@ paradox
 =======
 
 Package website: [release](https://paradox.mlr-org.com/) \|
-[dev](https://paradox.mlr-org.com/dev)
+[dev](https://paradox.mlr-org.com/dev/)
 
 Universal Parameter Space Description and Tools.
 
@@ -84,26 +84,26 @@ Properties of the parameters within the `ParamSet`:
     ps$levels
     #> $z
     #> NULL
-    #> 
+    #>
     #> $x
     #> NULL
-    #> 
+    #>
     #> $flag
     #> [1]  TRUE FALSE
-    #> 
+    #>
     #> $methods
     #> [1] "a" "b" "c"
     ps$nlevels
-    #>       z       x    flag methods 
+    #>       z       x    flag methods
     #>       3     Inf       2       3
     ps$is_number
-    #>       z       x    flag methods 
+    #>       z       x    flag methods
     #>    TRUE    TRUE   FALSE   FALSE
     ps$lower
-    #>       z       x    flag methods 
+    #>       z       x    flag methods
     #>       1     -10      NA      NA
     ps$upper
-    #>       z       x    flag methods 
+    #>       z       x    flag methods
     #>       3      10      NA      NA
 
 ### Parameter Checks
@@ -151,15 +151,15 @@ inside the transformation.
     #> [[1]]
     #> [[1]]$z
     #> [1] 0.125
-    #> 
+    #>
     #> [[1]]$x
     #> [1] 0.4137243
-    #> 
-    #> 
+    #>
+    #>
     #> [[2]]
     #> [[2]]$z
     #> [1] 0.5
-    #> 
+    #>
     #> [[2]]$x
     #> [1] 0.3688455