diff --git a/e2fsprogs/blkid/probe.c b/e2fsprogs/blkid/probe.c
index 5ee8a200e..03bbc749c 100644
--- a/e2fsprogs/blkid/probe.c
+++ b/e2fsprogs/blkid/probe.c
@@ -98,7 +98,7 @@ static void get_ext2_info(blkid_dev dev, unsigned char *buf)
 static int probe_ext3(int fd __BLKID_ATTR((unused)),
 		      blkid_cache cache __BLKID_ATTR((unused)),
 		      blkid_dev dev,
-		      struct blkid_magic *id __BLKID_ATTR((unused)), 
+		      const struct blkid_magic *id __BLKID_ATTR((unused)), 
 		      unsigned char *buf)
 {
 	struct ext2_super_block *es;
@@ -125,7 +125,7 @@ static int probe_ext3(int fd __BLKID_ATTR((unused)),
 static int probe_ext2(int fd __BLKID_ATTR((unused)),
 		      blkid_cache cache __BLKID_ATTR((unused)),
 		      blkid_dev dev,
-		      struct blkid_magic *id __BLKID_ATTR((unused)), 
+		      const struct blkid_magic *id __BLKID_ATTR((unused)), 
 		      unsigned char *buf)
 {
 	struct ext2_super_block *es;
@@ -307,7 +307,7 @@ static int probe_romfs(int fd __BLKID_ATTR((unused)),
 static int probe_cramfs(int fd __BLKID_ATTR((unused)), 
 		       blkid_cache cache __BLKID_ATTR((unused)), 
 		       blkid_dev dev,
-		       struct blkid_magic *id __BLKID_ATTR((unused)), 
+		       const struct blkid_magic *id __BLKID_ATTR((unused)), 
 		       unsigned char *buf)
 {
 	struct cramfs_super_block *csb;