diff --git a/R/missRanger.R b/R/missRanger.R
index abfc9df..f1e3c13 100644
--- a/R/missRanger.R
+++ b/R/missRanger.R
@@ -375,8 +375,14 @@ convert <- function(X, check = FALSE) {
   stopifnot(is.data.frame(X))
   
   if (!ncol(X)) {
-    return(list(X = X, bad = character(0), vars = character(0), 
-                types = character(0), classes = character(0)))
+    out <- list(
+      X = X, 
+      bad = character(0), 
+      vars = character(0), 
+      types = character(0), 
+      classes = character(0)
+    )
+    return(out)
   }
   
   types <- vapply(X, typeof2, FUN.VALUE = "")
diff --git a/R/pmm.R b/R/pmm.R
index 3734772..70ec638 100644
--- a/R/pmm.R
+++ b/R/pmm.R
@@ -22,12 +22,14 @@
 #' pmm(xtrain = c("A", "A", "B"), xtest = "A", ytrain = c(2, 2, 4), k = 2) # 2
 #' pmm(xtrain = factor(c("A", "B")), xtest = factor("C"), ytrain = 1:2) # 2
 pmm <- function(xtrain, xtest, ytrain, k = 1L, seed = NULL) {
-  stopifnot(length(xtrain) == length(ytrain), 
-            sum(ok <- !is.na(xtrain) & !is.na(ytrain)) >= 1L,
-            (nt <- length(xtest)) >= 1L, !anyNA(xtest),
-            mode(xtrain) %in% c("logical", "numeric", "character"),
-            mode(xtrain) == mode(xtest),
-            k >= 1L)
+  stopifnot(
+    length(xtrain) == length(ytrain), 
+    sum(ok <- !is.na(xtrain) & !is.na(ytrain)) >= 1L,
+    (nt <- length(xtest)) >= 1L, !anyNA(xtest),
+    mode(xtrain) %in% c("logical", "numeric", "character"),
+    mode(xtrain) == mode(xtest),
+    k >= 1L
+  )
   
   xtrain <- xtrain[ok]
   ytrain <- ytrain[ok]
diff --git a/tests/testthat/test-missRanger.R b/tests/testthat/test-missRanger.R
index 06e9bf6..ecb07ba 100644
--- a/tests/testthat/test-missRanger.R
+++ b/tests/testthat/test-missRanger.R
@@ -208,3 +208,26 @@ test_that("Extremely wide datasets are handled", {
   data[5L, 5L] <- NA
   expect_no_error(missRanger(as.data.frame(data), num.trees = 3L, verbose = 0L))
 })
+
+test_that("Convert and revert do what they should", {
+  n <- 20L
+  X <- data.frame(
+    x1 = seq_len(n), 
+    x2 = rep(LETTERS[1:4], n %/% 4),
+    x3 = factor(rep(LETTERS[1:2], n %/% 2)),
+    x4 = seq_len(n) > n %/% 3,
+    x5 = seq(as.Date("2008-11-01"), as.Date("2008-11-21"), length.out = n)
+  )
+  X <- generateNA(X, seed = 1L)
+  conv <- convert(X)
+  reve <- revert(conv)
+  
+  expect_equal(X, reve)
+  expect_equal(
+    unname(sapply(conv$X, class)), 
+    c("integer", "factor", "factor", "factor", "numeric")
+  )
+  
+  Ximp <- missRanger(X, seed = 1L, verbose = FALSE, pmm.k = 3L)
+  expect_equal(sapply(Ximp, class), sapply(X, class))
+})