diff --git a/src/core/uuid.c b/src/core/uuid.c
index b8d21de17..c43d4216f 100644
--- a/src/core/uuid.c
+++ b/src/core/uuid.c
@@ -40,7 +40,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  * @v uuid		UUID
  * @ret string		UUID in canonical form
  */
-char * uuid_ntoa ( const union uuid *uuid ) {
+const char * uuid_ntoa ( const union uuid *uuid ) {
 	static char buf[37]; /* "00000000-0000-0000-0000-000000000000" */
 
 	sprintf ( buf, "%08x-%04x-%04x-%04x-%02x%02x%02x%02x%02x%02x",
diff --git a/src/include/ipxe/uuid.h b/src/include/ipxe/uuid.h
index 6c45eb9aa..24c46acaf 100644
--- a/src/include/ipxe/uuid.h
+++ b/src/include/ipxe/uuid.h
@@ -47,6 +47,6 @@ static inline void uuid_mangle ( union uuid *uuid ) {
 	__bswap_16s ( &uuid->canonical.c );
 }
 
-extern char * uuid_ntoa ( const union uuid *uuid );
+extern const char * uuid_ntoa ( const union uuid *uuid );
 
 #endif /* _IPXE_UUID_H */
diff --git a/src/net/peerdisc.c b/src/net/peerdisc.c
index 5b0e98911..4c3cd2ea5 100644
--- a/src/net/peerdisc.c
+++ b/src/net/peerdisc.c
@@ -408,7 +408,7 @@ static struct peerdisc_segment * peerdisc_create ( const char *id ) {
 	} random_uuid;
 	size_t uuid_len;
 	size_t id_len;
-	char *uuid;
+	const char *uuid;
 	char *uuid_copy;
 	char *id_copy;
 	unsigned int i;