diff --git a/ruby-parser-cpp/src/decoder.rs b/ruby-parser-cpp/src/decoder.rs
index 45fec87..541f00f 100644
--- a/ruby-parser-cpp/src/decoder.rs
+++ b/ruby-parser-cpp/src/decoder.rs
@@ -1,4 +1,5 @@
 #[allow(unused_imports)]
+use std::os::raw::{c_char};
 use crate::{blob_type, bytes::ByteListBlob, string::StringBlob};
 use lib_ruby_parser::source::{DecoderResult, InputError};
 
@@ -73,7 +74,7 @@ pub extern "C" fn lib_ruby_parser__test__always_ok_decoder(output: *const u8) ->
         drop(String::from(encoding));
         drop(Vec::<u8>::from(input));
         // and return given output
-        let output = unsafe { std::ffi::CStr::from_ptr(state as *const i8) }
+        let output = unsafe { std::ffi::CStr::from_ptr(state as *const c_char) }
             .to_str()
             .unwrap();
         DecoderResultBlob::from(DecoderResult::Ok(output.as_bytes().to_vec()))
@@ -97,7 +98,7 @@ pub extern "C" fn lib_ruby_parser__test__always_err_decoder(output: *const u8) -
         drop(String::from(encoding));
         drop(Vec::<u8>::from(input));
         // and return given output
-        let output = unsafe { std::ffi::CStr::from_ptr(state as *const i8) }
+        let output = unsafe { std::ffi::CStr::from_ptr(state as *const c_char) }
             .to_str()
             .unwrap();
         DecoderResultBlob::from(DecoderResult::Err(InputError::DecodingError(
diff --git a/ruby-parser-cpp/src/diagnostic.rs b/ruby-parser-cpp/src/diagnostic.rs
index 706f06a..f638357 100644
--- a/ruby-parser-cpp/src/diagnostic.rs
+++ b/ruby-parser-cpp/src/diagnostic.rs
@@ -1,3 +1,4 @@
+use std::os::raw::{c_char};
 use crate::blob_type;
 #[allow(unused_imports)]
 use crate::message::DiagnosticMessageBlob;
@@ -42,7 +43,7 @@ pub extern "C" fn LIB_RUBY_PARSER_drop_diagnostic_list(diagnostic_list: *mut Vec
 pub extern "C" fn LIB_RUBY_PARSER_render_diagnostic(
     diagnostic: *const Diagnostic,
     input: *const DecodedInput,
-) -> *mut i8 {
+) -> *mut c_char {
     let diagnostic = unsafe { diagnostic.as_ref().unwrap() };
     let input = unsafe { input.as_ref().unwrap() };
     let rendered = diagnostic.render(input).unwrap();
diff --git a/ruby-parser-cpp/src/loc.rs b/ruby-parser-cpp/src/loc.rs
index 0fb6179..4cd0ae3 100644
--- a/ruby-parser-cpp/src/loc.rs
+++ b/ruby-parser-cpp/src/loc.rs
@@ -1,3 +1,4 @@
+use std::os::raw::{c_char};
 use crate::blob_type;
 use lib_ruby_parser::source::DecodedInput;
 #[allow(unused_imports)]
@@ -27,7 +28,7 @@ pub extern "C" fn lib_ruby_parser__test__make_some_loc(begin: usize, end: usize)
 pub extern "C" fn LIB_RUBY_PARSER_loc_source(
     loc: *const Loc,
     input: *const DecodedInput,
-) -> *mut i8 {
+) -> *mut c_char {
     let loc = unsafe { loc.as_ref().unwrap() };
     let input = unsafe { input.as_ref().unwrap() };
     let source = loc.source(input).unwrap();
diff --git a/ruby-parser-cpp/src/string.rs b/ruby-parser-cpp/src/string.rs
index 50e41e9..0cb5d52 100644
--- a/ruby-parser-cpp/src/string.rs
+++ b/ruby-parser-cpp/src/string.rs
@@ -1,4 +1,5 @@
 use crate::blob_type;
+use std::os::raw::{c_char};
 
 blob_type!(StringBlob, String);
 blob_type!(MaybeStringBlob, Option<String>);
@@ -10,7 +11,7 @@ pub extern "C" fn LIB_RUBY_PARSER_new_string_owned(ptr: *mut u8, len: usize) ->
 }
 
 #[no_mangle]
-pub extern "C" fn LIB_RUBY_PARSER_new_string_from_cstr(ptr: *const i8) -> StringBlob {
+pub extern "C" fn LIB_RUBY_PARSER_new_string_from_cstr(ptr: *const c_char) -> StringBlob {
     let s = unsafe { std::ffi::CStr::from_ptr(ptr) };
     StringBlob::from(s.to_str().unwrap_or_default().to_owned())
 }
diff --git a/ruby-parser-cpp/src/token.rs b/ruby-parser-cpp/src/token.rs
index aadb14e..5cbd8f2 100644
--- a/ruby-parser-cpp/src/token.rs
+++ b/ruby-parser-cpp/src/token.rs
@@ -1,3 +1,4 @@
+use std::os::raw::{c_char};
 use crate::blob_type;
 #[allow(unused_imports)]
 use lib_ruby_parser::{Bytes, LexState, Lexer, Loc, Token};
@@ -29,7 +30,7 @@ pub extern "C" fn lib_ruby_parser__test__make_token_eq(
 }
 
 #[no_mangle]
-pub extern "C" fn LIB_RUBY_PARSER_token_name(token: *const Token) -> *mut i8 {
+pub extern "C" fn LIB_RUBY_PARSER_token_name(token: *const Token) -> *mut c_char {
     let token = unsafe { token.as_ref().unwrap() };
     let token_name = token.token_name();
     std::ffi::CString::new(token_name).unwrap().into_raw()