diff --git a/src/protocol/auth/auth.c b/src/protocol/auth/auth.c
index dfb3ddae..411afa92 100644
--- a/src/protocol/auth/auth.c
+++ b/src/protocol/auth/auth.c
@@ -33,7 +33,7 @@ static INIT_LIST_OF(struct auth_entry, auth_entry_list);
  * NULL, it returns the first record found. If realm isn't NULL, it returns
  * the first record that matches exactly (url and realm) if any. */
 static struct auth_entry *
-find_auth_entry(struct uri *uri, char *realm)
+find_auth_entry(struct uri *uri, const char *realm)
 {
 	struct auth_entry *match = NULL, *entry;
 
@@ -92,7 +92,7 @@ set_auth_password(struct auth_entry *entry, struct uri *uri)
 static void done_auth_entry(struct auth_entry *entry);
 
 static struct auth_entry *
-init_auth_entry(struct uri *uri, char *realm)
+init_auth_entry(struct uri *uri, const char *realm)
 {
 	struct auth_entry *entry;
 
@@ -132,7 +132,7 @@ init_auth_entry(struct uri *uri, char *realm)
 /* Returns the new entry or updates an existing one. Sets the @valid member if
  * updating is required so it can be tested if the user should be queried. */
 struct auth_entry *
-add_auth_entry(struct uri *uri, char *realm, char *nonce,
+add_auth_entry(struct uri *uri, const char *realm, char *nonce,
 	char *opaque, unsigned int digest)
 {
 	struct auth_entry *entry;
diff --git a/src/protocol/auth/auth.h b/src/protocol/auth/auth.h
index f238f7fd..364afe1f 100644
--- a/src/protocol/auth/auth.h
+++ b/src/protocol/auth/auth.h
@@ -42,7 +42,7 @@ struct auth_entry {
 	(*(_entry_)->user || *(_entry_)->password)
 
 struct auth_entry *find_auth(struct uri *);
-struct auth_entry *add_auth_entry(struct uri *, char *,
+struct auth_entry *add_auth_entry(struct uri *, const char *,
 	char *, char *, unsigned int);
 void del_auth_entry(struct auth_entry *);
 void free_auth(void);