diff --git a/include/tree_sitter/runtime.h b/include/tree_sitter/runtime.h
index 270800d4..4ab55ae0 100644
--- a/include/tree_sitter/runtime.h
+++ b/include/tree_sitter/runtime.h
@@ -16,7 +16,7 @@ typedef struct {
 typedef struct {
   void *payload;
   const char *(*read_fn)(void *payload, size_t *bytes_read);
-  int (*seek_fn)(void *payload, TSLength position);
+  int (*seek_fn)(void *payload, size_t character, size_t byte);
 } TSInput;
 
 typedef enum {
diff --git a/spec/runtime/helpers/spy_input.cc b/spec/runtime/helpers/spy_input.cc
index 764ae8ed..8d7ebdaf 100644
--- a/spec/runtime/helpers/spy_input.cc
+++ b/spec/runtime/helpers/spy_input.cc
@@ -84,11 +84,11 @@ const char * SpyInput::read(void *payload, size_t *bytes_read) {
   return spy->buffer;
 }
 
-int SpyInput::seek(void *payload, TSLength position) {
+int SpyInput::seek(void *payload, size_t character, size_t byte) {
   auto spy = static_cast<SpyInput *>(payload);
   if (spy->strings_read.size() == 0 || spy->strings_read.back().size() > 0)
     spy->strings_read.push_back("");
-  spy->byte_offset = position.bytes;
+  spy->byte_offset = byte;
   return 0;
 }
 
diff --git a/spec/runtime/helpers/spy_input.h b/spec/runtime/helpers/spy_input.h
index b5f02eef..b2a0249c 100644
--- a/spec/runtime/helpers/spy_input.h
+++ b/spec/runtime/helpers/spy_input.h
@@ -19,7 +19,7 @@ class SpyInput {
   std::vector<SpyInputEdit> undo_stack;
 
   static const char * read(void *, size_t *);
-  static int seek(void *, TSLength);
+  static int seek(void *, size_t, size_t);
   std::string swap_substr(size_t, size_t, std::string);
 
  public:
diff --git a/src/runtime/lexer.c b/src/runtime/lexer.c
index bc6b5bd9..b443082c 100644
--- a/src/runtime/lexer.c
+++ b/src/runtime/lexer.c
@@ -24,7 +24,7 @@ static void ts_lexer__get_chunk(TSLexer *self) {
   TSInput input = self->input;
   if (!self->chunk ||
       self->current_position.bytes != self->chunk_start + self->chunk_size)
-    input.seek_fn(input.payload, self->current_position);
+    input.seek_fn(input.payload, self->current_position.chars, self->current_position.bytes);
 
   self->chunk_start = self->current_position.bytes;
   self->chunk = input.read_fn(input.payload, &self->chunk_size);
diff --git a/src/runtime/string_input.c b/src/runtime/string_input.c
index d964ef40..5f91e759 100644
--- a/src/runtime/string_input.c
+++ b/src/runtime/string_input.c
@@ -19,10 +19,10 @@ const char *ts_string_input_read(void *payload, size_t *bytes_read) {
   return input->string + previous_position;
 }
 
-int ts_string_input_seek(void *payload, TSLength position) {
+int ts_string_input_seek(void *payload, size_t character, size_t byte) {
   TSStringInput *input = (TSStringInput *)payload;
-  input->position = position.bytes;
-  return (position.bytes < input->length);
+  input->position = byte;
+  return (byte < input->length);
 }
 
 TSInput ts_string_input_make(const char *string) {