diff --git a/luna/Types.h b/luna/Types.h
index a872a576..0abcefa7 100644
--- a/luna/Types.h
+++ b/luna/Types.h
@@ -10,7 +10,7 @@ typedef int16_t i16;
 typedef int32_t i32;
 typedef int64_t i64;
 typedef size_t usize;
-typedef long isize;
+typedef int64_t isize;
 
 static_assert(sizeof(u8) == 1UL);
 static_assert(sizeof(u16) == 2UL);