diff --git a/DESCRIPTION b/DESCRIPTION
index 72fa79b2e..08eae06d1 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -2,7 +2,7 @@ Package: polars
 Title: Lightning-Fast 'DataFrame' Library
 Version: 0.14.1.9000
 Depends: R (>= 4.2)
-Imports: utils, codetools
+Imports: utils, codetools, methods
 Authors@R:
   c(person("Ritchie", "Vink", , "ritchie46@gmail.com", role = c("aut")),
     person("Soren", "Welling", , "sorhawell@gmail.com", role = c("aut", "cre")),
diff --git a/NAMESPACE b/NAMESPACE
index 56b81cfc9..49c04156d 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -263,6 +263,7 @@ export(polars_envvars)
 export(polars_info)
 export(polars_options)
 export(polars_options_reset)
+importFrom(methods,new)
 importFrom(stats,median)
 importFrom(stats,na.omit)
 importFrom(utils,.DollarNames)
diff --git a/NEWS.md b/NEWS.md
index f364703cd..22babf2de 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -49,6 +49,12 @@
 -   Converts `clock_time_point` and `clock_zoned_time` objects from
     the `{clock}` package to Polars datetime type (#861).
 
+### Bug fixes
+
+-   R no longer crashes when calling an invalid Polars object that points
+    to a null pointer (#874). This was occurring, such as when a Polars object
+    was saved in an RDS file and loaded from another session.
+
 ## Polars R Package 0.14.1
 
 ### Breaking changes
diff --git a/R/after-wrappers.R b/R/after-wrappers.R
index 0b632991e..9d4f18544 100644
--- a/R/after-wrappers.R
+++ b/R/after-wrappers.R
@@ -142,10 +142,11 @@ extendr_method_to_pure_functions = function(env, class_name = NULL) {
 macro_add_syntax_check_to_class = function(Class_name) {
   tokens = paste0(
     "`$.", Class_name, "` <- function (self, name) {\n",
-    "  verify_method_call(", Class_name, ",name)\n",
+    "  verify_not_null_pointer(self, 'in `$.", Class_name, "`')\n",
+    "  verify_method_call(", Class_name, ", name)\n",
     "  func <- ", Class_name, "[[name]]\n",
     "  environment(func) <- environment()\n",
-    "  if(inherits(func,'property')) {\n",
+    "  if(inherits(func, 'property')) {\n",
     "    func()\n",
     "  } else {\n",
     "   func\n",
@@ -329,8 +330,6 @@ pl_mem_address = function(robj) {
 #'  - Code completion is facilitated by `.DollarNames.ClassName`-s3method see e.g. 'R/dataframe__frame.R'
 #'  - Implementation of property-methods as DataFrame_columns() and syntax checking is an extension to `$.ClassName`
 #'  See function macro_add_syntax_check_to_class().
-#'
-#' @importFrom utils .DollarNames
 #' @return not applicable
 #' @examples
 #' # all a polars object is only made of:
diff --git a/R/pkg-knitr.R b/R/pkg-knitr.R
index 8eaa6e9c7..c2db90f76 100644
--- a/R/pkg-knitr.R
+++ b/R/pkg-knitr.R
@@ -41,7 +41,6 @@ knit_print.RPolarsDataFrame = function(x, ...) {
 #' @examples
 #' to_html_table(mtcars, 3, 3)
 #' @noRd
-#' @importFrom utils getFromNamespace
 to_html_table = function(x, max_cols = 75, max_rows = 40) {
   if (!requireNamespace("knitr", quietly = TRUE)) {
     stop("Please install the `knitr` package to use `to_html_table`.")
diff --git a/R/polars-package.R b/R/polars-package.R
index 4ecd80114..8740259e2 100644
--- a/R/polars-package.R
+++ b/R/polars-package.R
@@ -2,7 +2,9 @@
 "_PACKAGE"
 
 ## usethis namespace: start
-#' @importFrom utils globalVariables head tail download.file capture.output str
+#' @importFrom stats na.omit median
+#' @importFrom utils .DollarNames globalVariables getFromNamespace head tail download.file capture.output str
+#' @importFrom methods new
 ## usethis namespace: end
 NULL
 
diff --git a/R/s3_methods.R b/R/s3_methods.R
index 49e95175f..8a2b8dd04 100644
--- a/R/s3_methods.R
+++ b/R/s3_methods.R
@@ -341,16 +341,13 @@ mean.RPolarsSeries = function(x, ...) x$mean()
 #'
 #' @export
 #' @rdname S3_median
-#' @importFrom stats median
 median.RPolarsDataFrame = function(x, ...) x$median()
 
 #' @export
-#' @importFrom stats median
 #' @rdname S3_median
 median.RPolarsLazyFrame = function(x, ...) x$median()
 
 #' @export
-#' @importFrom stats median
 #' @rdname S3_median
 median.RPolarsSeries = function(x, ...) x$median()
 
@@ -494,8 +491,6 @@ c.RPolarsSeries = \(x, ...) {
 #' @param object A [DataFrame][DataFrame_class] or [LazyFrame][LazyFrame_class]
 #' @param subset Character vector of column names to drop missing values from.
 #' @param ... Not used.
-#'
-#' @importFrom stats na.omit
 #' @export
 #' @rdname S3_na.omit
 #' @examples
diff --git a/R/utils.R b/R/utils.R
index fbf8c87f7..9fec4b827 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -49,7 +49,34 @@ check_no_missing_args = function(
 }
 
 
+# https://stackoverflow.com/a/27350487/3297472
+is_null_external_pointer = function(pointer) {
+  a = attributes(pointer)
+  attributes(pointer) = NULL
+  out = identical(pointer, new("externalptr"))
+  attributes(pointer) = a
+  out
+}
+
 
+verify_not_null_pointer = function(pointer, context = NULL) {
+  valid = FALSE
+  tryCatch(
+    {
+      valid = !is_null_external_pointer(pointer)
+    },
+    error = function(c) {}
+  )
+
+  if (!valid) {
+    Err_plain(
+      "This Polars object is not valid. Execute `rm(<object>)` to remove the object or restart the R session."
+    ) |>
+      unwrap(context = context)
+  }
+
+  invisible(NULL)
+}
 
 
 #' Verify user selected method/attribute exists
diff --git a/tests/testthat/test-after-wrappers.R b/tests/testthat/test-after-wrappers.R
index 8c9ce761c..95eafb888 100644
--- a/tests/testthat/test-after-wrappers.R
+++ b/tests/testthat/test-after-wrappers.R
@@ -32,3 +32,10 @@ patrick::with_parameters_test_that("public and private methods of each class",
   },
   .cases = make_class_cases()
 )
+
+
+test_that("check the polars object is valid", {
+  raw = as_polars_df(mtcars) |>
+    serialize(connection = NULL)
+  expect_error(print(unserialize(raw)), "restart the R session")
+})