diff --git a/src/parser/parser.l b/src/parser/parser.l
index 0e4325f..2a1f43a 100644
--- a/src/parser/parser.l
+++ b/src/parser/parser.l
@@ -5,9 +5,12 @@
 
 #include "parser.h"
 #include "parser.tab.h"
+#include "String.h"
 
 #define YY_USER_ACTION yylloc->first_column += yyleng;
 
+static String * build_string = NULL;
+
 %}
 
 %x str
@@ -97,21 +100,30 @@ sizeof              return TOK_SIZEOF;
 0[xX][0-9a-fA-F]+([uU][lL]?[lL]?)?   return TOK_INT_CONST;
 [0-9]*\.[0-9]*[fF]? return TOK_FLOAT_CONST;
 
-\"                  BEGIN(str);
+\" {
+    if (build_string != NULL)
+    {
+        String_free(build_string);
+    }
+    build_string = String_new("");
+    BEGIN(str);
+}
 <str>{
 \"                  return TOK_STR_CONST;
 \\x[0-9A-Fa-f]{2} {
                     /* hexadecimal escape code */
                     unsigned int val;
                     (void) sscanf(yytext + 2, "%x", &val);
+                    char v[2] = {(char)val, '\0'};
+                    String_concat(build_string, v);
 }
-\\n                 (void)'\n';
-\\t                 (void)'\t';
-\\r                 (void)'\r';
-\\b                 (void)'\b';
-\\f                 (void)'\f';
-\\.                 (void)yytext[1];
-[^\\\"]+            (void)yytext;
+\\n                 String_concat(build_string, "\n");
+\\t                 String_concat(build_string, "\t");
+\\r                 String_concat(build_string, "\r");
+\\b                 String_concat(build_string, "\b");
+\\f                 String_concat(build_string, "\f");
+\\.                 String_concat(build_string, &yytext[1]);
+[^\\\"]+            String_concat(build_string, yytext);
 }
 
 [a-zA-Z_][a-zA-Z_0-9]*              return TOK_IDENTIFIER;