diff --git a/compiler/lex.c b/compiler/lex.c
index 0c18e4b..aa0bc5b 100644
--- a/compiler/lex.c
+++ b/compiler/lex.c
@@ -15,7 +15,7 @@
 #define STRING_LITERAL_BASE_SIZE 255
 #define STRING_LITERAL_MAX_SIZE 4096
 
-#define at_buffer_end(ls) (*(ls)->fwd == '\0')
+#define at_buffer_end(ls) (*(ls)->fwd == LEX_BUFFER_SENTINEL)
 #define ascii_isident(c) (c == '_' || c == '?' || c == '!' || ascii_isalnum(c))
 #define ascii_isident_start(c) (c == '_' || ascii_isalpha(c))