diff --git a/include/cxx.h b/include/cxx.h
index 4e261a355..65c91b89b 100644
--- a/include/cxx.h
+++ b/include/cxx.h
@@ -14,11 +14,6 @@
 #include <type_traits>
 #include <utility>
 #include <vector>
-#if defined(_WIN32)
-#include <basetsd.h>
-#else
-#include <sys/types.h>
-#endif
 
 #if __cplusplus >= 201703L
 #include <string_view>
@@ -442,11 +437,7 @@ class Error final : public std::exception {
 
 #ifndef CXXBRIDGE1_RUST_ISIZE
 #define CXXBRIDGE1_RUST_ISIZE
-#if defined(_WIN32)
-using isize = SSIZE_T;
-#else
-using isize = ssize_t;
-#endif
+using isize = intptr_t;
 #endif // CXXBRIDGE1_RUST_ISIZE
 
 std::ostream &operator<<(std::ostream &, const String &);