diff --git a/src/iri.c b/src/iri.c
index 9660f185..a6b1c6e2 100644
--- a/src/iri.c
+++ b/src/iri.c
@@ -53,8 +53,9 @@ as that of the covered work.  */
 /* Given a string containing "charset=XXX", return the encoding if found,
    or NULL otherwise */
 char *
-parse_charset (char *str)
+parse_charset (const char *str)
 {
+  const char *end;
   char *charset;
 
   if (!str || !*str)
@@ -65,14 +66,14 @@ parse_charset (char *str)
     return NULL;
 
   str += 8;
-  charset = str;
+  end = str;
 
   /* sXXXav: which chars should be banned ??? */
-  while (*charset && !c_isspace (*charset))
-    charset++;
+  while (*end && !c_isspace (*end))
+    end++;
 
   /* sXXXav: could strdupdelim return NULL ? */
-  charset = strdupdelim (str, charset);
+  charset = strdupdelim (str, end);
 
   /* Do a minimum check on the charset value */
   if (!check_encoding_name (charset))
@@ -95,9 +96,9 @@ find_locale (void)
 
 /* Basic check of an encoding name. */
 bool
-check_encoding_name (char *encoding)
+check_encoding_name (const char *encoding)
 {
-  char *s = encoding;
+  const char *s = encoding;
 
   while (*s)
     {
@@ -266,7 +267,7 @@ _utf8_is_valid(const char *utf8)
 /* Try to "ASCII encode" UTF-8 host. Return the new domain on success or NULL
    on error. */
 char *
-idn_encode (struct iri *i, char *host)
+idn_encode (const struct iri *i, const char *host)
 {
   int ret;
   char *ascii_encoded;
@@ -304,7 +305,7 @@ idn_encode (struct iri *i, char *host)
 /* Try to decode an "ASCII encoded" host. Return the new domain in the locale
    on success or NULL on error. */
 char *
-idn_decode (char *host)
+idn_decode (const char *host)
 {
   char *new;
   int ret;
@@ -323,7 +324,7 @@ idn_decode (char *host)
 /* Try to transcode string str from remote encoding to UTF-8. On success, *new
    contains the transcoded string. *new content is unspecified otherwise. */
 bool
-remote_to_utf8 (struct iri *iri, const char *str, char **new)
+remote_to_utf8 (const struct iri *iri, const char *str, char **new)
 {
   bool ret = false;
 
@@ -397,7 +398,7 @@ iri_free (struct iri *i)
 /* Set uri_encoding of struct iri i. If a remote encoding was specified, use
    it unless force is true. */
 void
-set_uri_encoding (struct iri *i, char *charset, bool force)
+set_uri_encoding (struct iri *i, const char *charset, bool force)
 {
   DEBUGP (("URI encoding = %s\n", charset ? quote (charset) : "None"));
   if (!force && opt.encoding_remote)
@@ -414,7 +415,7 @@ set_uri_encoding (struct iri *i, char *charset, bool force)
 
 /* Set content_encoding of struct iri i. */
 void
-set_content_encoding (struct iri *i, char *charset)
+set_content_encoding (struct iri *i, const char *charset)
 {
   DEBUGP (("URI content encoding = %s\n", charset ? quote (charset) : "None"));
   if (opt.encoding_remote)
diff --git a/src/iri.h b/src/iri.h
index 8ba50b22..81f7ce83 100644
--- a/src/iri.h
+++ b/src/iri.h
@@ -43,18 +43,18 @@ struct iri {
 # include <idna.h>
 # include <idn-free.h>
 
-char *parse_charset (char *str);
+char *parse_charset (const char *str);
 char *find_locale (void);
-bool check_encoding_name (char *encoding);
+bool check_encoding_name (const char *encoding);
 const char *locale_to_utf8 (const char *str);
-char *idn_encode (struct iri *i, char *host);
-char *idn_decode (char *host);
-bool remote_to_utf8 (struct iri *i, const char *str, char **new);
+char *idn_encode (const struct iri *i, const char *host);
+char *idn_decode (const char *host);
+bool remote_to_utf8 (const struct iri *i, const char *str, char **new);
 struct iri *iri_new (void);
 struct iri *iri_dup (const struct iri *);
 void iri_free (struct iri *i);
-void set_uri_encoding (struct iri *i, char *charset, bool force);
-void set_content_encoding (struct iri *i, char *charset);
+void set_uri_encoding (struct iri *i, const char *charset, bool force);
+void set_content_encoding (struct iri *i, const char *charset);
 
 #else /* ENABLE_IRI */