diff --git a/src/parser/parser.l b/src/parser/parser.l
index e68b5c7..73bcaa5 100644
--- a/src/parser/parser.l
+++ b/src/parser/parser.l
@@ -143,7 +143,7 @@ L?\" {
                     char v[2] = {(char)val, '\0'};
                     String_concat(build_string, v);
 }
-\\[0-7][0-7]?[0-7]? {
+\\[0-7]{1,3} {
                     /* octal escape code */
                     unsigned int val;
                     (void)sscanf(yytext + 1, "%o", &val);