diff --git a/src/runtime/lexer.c b/src/runtime/lexer.c
index 123a29fd..5646e101 100644
--- a/src/runtime/lexer.c
+++ b/src/runtime/lexer.c
@@ -36,11 +36,17 @@ static void ts_lexer__get_lookahead(Lexer *self) {
   const uint8_t *chunk = (const uint8_t *)self->chunk + position_in_chunk;
   uint32_t size = self->chunk_size - position_in_chunk + 1;
 
-  if (self->input.encoding == TSInputEncodingUTF8)
-    self->lookahead_size =
-      utf8proc_iterate(chunk, size, &self->data.lookahead);
-  else
+  if (self->input.encoding == TSInputEncodingUTF8) {
+    int64_t lookahead_size = utf8proc_iterate(chunk, size, &self->data.lookahead);
+    if (lookahead_size < 0) {
+      self->lookahead_size = 1;
+    } else {
+      self->lookahead_size = lookahead_size;
+    }
+  }
+  else {
     self->lookahead_size = utf16_iterate(chunk, size, &self->data.lookahead);
+  }
 }
 
 static void ts_lexer__advance(void *payload, bool skip) {
diff --git a/src/runtime/tree.c b/src/runtime/tree.c
index 49f81e9c..195b6260 100644
--- a/src/runtime/tree.c
+++ b/src/runtime/tree.c
@@ -99,7 +99,7 @@ TreeArray ts_tree_array_remove_trailing_extras(TreeArray *self) {
   return result;
 }
 
-Tree *ts_tree_make_error(Length size, Length padding, char lookahead_char) {
+Tree *ts_tree_make_error(Length size, Length padding, int32_t lookahead_char) {
   Tree *result = ts_tree_make_leaf(ts_builtin_sym_error, padding, size,
                                      (TSSymbolMetadata){
                                        .visible = true, .named = true,
diff --git a/src/runtime/tree.h b/src/runtime/tree.h
index c08ba24b..f205af97 100644
--- a/src/runtime/tree.h
+++ b/src/runtime/tree.h
@@ -76,7 +76,7 @@ Tree *ts_tree_make_leaf(TSSymbol, Length, Length, TSSymbolMetadata);
 Tree *ts_tree_make_node(TSSymbol, uint32_t, Tree **, TSSymbolMetadata);
 Tree *ts_tree_make_copy(Tree *child);
 Tree *ts_tree_make_error_node(TreeArray *);
-Tree *ts_tree_make_error(Length, Length, char);
+Tree *ts_tree_make_error(Length, Length, int32_t);
 void ts_tree_retain(Tree *tree);
 void ts_tree_release(Tree *tree);
 bool ts_tree_eq(const Tree *tree1, const Tree *tree2);
diff --git a/test/helpers/encoding_helpers.cc b/test/helpers/encoding_helpers.cc
index 8ef9fec1..1169bb2d 100644
--- a/test/helpers/encoding_helpers.cc
+++ b/test/helpers/encoding_helpers.cc
@@ -4,10 +4,16 @@
 #include "utf8proc.h"
 
 static inline int string_iterate(TSInputEncoding encoding, const uint8_t *string, size_t length, int32_t *code_point) {
-  if (encoding == TSInputEncodingUTF8)
-    return utf8proc_iterate(string, length, code_point);
-  else
+  if (encoding == TSInputEncodingUTF8) {
+    int32_t character_size = utf8proc_iterate(string, length, code_point);
+    if (character_size < 0) {
+      return 1;
+    } else {
+      return character_size;
+    }
+  } else {
     return utf16_iterate(string, length, code_point);
+  }
 }
 
 size_t string_char_count(TSInputEncoding encoding, const std::string &input) {
diff --git a/test/runtime/parser_test.cc b/test/runtime/parser_test.cc
index 7dfcf26b..e390b164 100644
--- a/test/runtime/parser_test.cc
+++ b/test/runtime/parser_test.cc
@@ -473,6 +473,17 @@ describe("Parser", [&]() {
       AssertThat(ts_node_end_char(root), Equals(strlen("'OOO - DD';")));
       AssertThat(ts_node_end_byte(root), Equals(strlen("'\u03A9\u03A9\u03A9 \u2014 \u0394\u0394';")));
     });
+
+    it("handles non-UTF8 characters", [&]() {
+      const char *string = "cons\xeb\x00e=ls\x83l6hi');\x0a";
+
+      ts_document_set_language(document, load_real_language("javascript"));
+      ts_document_set_input_string(document, string);
+      ts_document_parse(document);
+
+      TSNode root = ts_document_root_node(document);
+      AssertThat(ts_node_end_byte(root), Equals(strlen(string)));
+    });
   });
 });