diff --git a/R/register.R b/R/register.R
index a7a1863e0..2e4c963d1 100644
--- a/R/register.R
+++ b/R/register.R
@@ -1,3 +1,12 @@
+maybe_encode_to_utf_8 <- function(a) {
+  b <- enc2utf8(a)
+  res <- iconv(b, from="UTF-8", to="UTF-8")
+  res
+}
+
+is_not_na <- function(x) {
+  !is.na(x)
+}
 # helper to clean up non-utf and posixlt vectors
 encode_values <- function(value) {
   if (!is.null(names(value))) {
@@ -5,7 +14,14 @@ encode_values <- function(value) {
   }
 
   is_character <- vapply(value, is.character, logical(1))
+  encoded_df <- lapply(value[is_character], maybe_encode_to_utf_8)
+  all_are_utf8 <- lapply(encoded_df[is_character], is_not_na)
+  if (!all(as.data.frame(all_are_utf8))) {
+    stop("not all values in the provided df are valid utf8")
+  }
+
   value[is_character] <- lapply(value[is_character], enc2utf8)
+
   is_factor <- vapply(value, is.factor, logical(1))
   value[is_factor] <- lapply(value[is_factor], function(x) {
     levels(x) <- enc2utf8(levels(x))
diff --git a/src/scan.cpp b/src/scan.cpp
index 14bc7581c..d53241c35 100644
--- a/src/scan.cpp
+++ b/src/scan.cpp
@@ -1,8 +1,8 @@
+#include "duckdb/main/client_context.hpp"
+#include "duckdb/third_party/utf8proc/include/utf8proc.hpp"
 #include "rapi.hpp"
 #include "typesr.hpp"
 
-#include "duckdb/main/client_context.hpp"
-
 using namespace duckdb;
 using namespace cpp11;
 
@@ -145,7 +145,6 @@ void AppendAnyColumnSegment(const RType &rtype, bool experimental, data_ptr_t co
 	}
 	case RType::STRING: {
 		auto data_ptr = (SEXP *)coldata_ptr;
-
 		if (experimental) {
 			D_ASSERT(v.GetType().id() == LogicalTypeId::POINTER);
 			AppendColumnSegment<SEXP, uintptr_t, DedupPointerEnumType>(data_ptr, sexp_offset, v, this_count);
diff --git a/tests/testthat/test_strings.R b/tests/testthat/test_strings.R
new file mode 100644
index 000000000..4d0fe27f2
--- /dev/null
+++ b/tests/testthat/test_strings.R
@@ -0,0 +1,14 @@
+library(duckdb)
+
+test_that("Invalid unicode produces an error", {
+  # this doesn't throw an error on old releases of R.
+  skip_if(R.Version()$major <= 4 && R.Version()$minor <= 2.3)
+  con <- DBI::dbConnect(duckdb::duckdb())
+
+  my_df <- structure(list(no_municipio_esc = "Est\xe2ncia", no_municipio_prova = "Est\xe2ncia"), row.names = 16L, class = "data.frame")
+  expect_error(dbWriteTable(con , 'my_table' , my_df ))
+
+  # test that the connection still works.
+  dbWriteTable(con, 'myTable', data.frame(a=c(1, 2, 3), b=c(4, 5, 6)))
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})