diff -ruN a/src/json.c b/src/json.c
--- a/src/json.c	2012-08-14 18:08:21.403880832 -0700
+++ b/src/json.c	2012-08-14 18:12:32.010823782 -0700
@@ -1370,7 +1370,7 @@
 
 
 int
-lexer (char *buffer, char **p, unsigned int *state, rcstring ** text, size_t *line)
+lexer (const char *buffer, const char **p, unsigned int *state, rcstring ** text, size_t *line)
 {
 	assert (buffer != NULL);
 	assert (p != NULL);
@@ -2133,7 +2133,7 @@
 
 
 enum json_error
-json_parse_fragment (struct json_parsing_info *info, char *buffer)
+json_parse_fragment (struct json_parsing_info *info, const char *buffer)
 {
 	json_t *temp = NULL;
 
@@ -2770,7 +2770,7 @@
 
 
 enum json_error
-json_parse_document (json_t ** root, char *text)
+json_parse_document (json_t ** root, const char *text)
 {
 	enum json_error error;
 	struct json_parsing_info *jpi;
diff -ruN a/src/json.h b/src/json.h
--- a/src/json.h	2012-08-14 18:08:21.403880832 -0700
+++ b/src/json.h	2012-08-14 18:10:51.622902467 -0700
@@ -108,7 +108,7 @@
 		unsigned int state;	/*!< the state where the parsing was left on the last parser run */
 		unsigned int lex_state;
 		rcstring *lex_text;
-		char *p;
+		const char *p;
 		int string_length_limit_reached;	/*!< flag informing if the string limit length defined by JSON_MAX_STRING_LENGTH was reached */
 		size_t line;	// current document line
 		json_t *cursor;	/*!< pointers to nodes belonging to the document tree which aid the document parsing */
@@ -303,7 +303,7 @@
 @param buffer a null-terminated c-string containing a JSON document fragment
 @return a code describing how the operation ended up
 **/
-	enum json_error json_parse_fragment (struct json_parsing_info *info, char *buffer);
+	enum json_error json_parse_fragment (struct json_parsing_info *info, const char *buffer);
 
 
 /**
@@ -312,7 +312,7 @@
 @param text a c-string containing a complete JSON text document
 @return a pointer to the new document tree or NULL if some error occurred
 **/
-	enum json_error json_parse_document (json_t ** root, char *text);
+	enum json_error json_parse_document (json_t ** root, const char *text);
 
 
 /**