diff --git a/luna/src/Utf8.cpp b/luna/src/Utf8.cpp
index 7ebc0c51..15930c2a 100644
--- a/luna/src/Utf8.cpp
+++ b/luna/src/Utf8.cpp
@@ -1,7 +1,8 @@
+#include <limits.h>
 #include <luna/CString.h>
 #include <luna/Utf8.h>
 
-static_assert(__WCHAR_MAX__ > 0x10ffff);
+static_assert(WCHAR_MAX > 0x10ffff);
 
 static Result<usize> utf8_char_length(char c)
 {