diff --git a/include/gint/fs.h b/include/gint/fs.h
index 9fd9205..6831dd2 100644
--- a/include/gint/fs.h
+++ b/include/gint/fs.h
@@ -78,7 +78,7 @@ void fs_free_descriptor(int fd);
    exact file descriptor reuse_fd is used. (This is useful to reopen standard
    streams.) In this case, the only possible return values are -1 and reuse_fd
    itself. */
-int open_generic(fs_descriptor_type_t *type, void *data, int reuse_fd);
+int open_generic(fs_descriptor_type_t const *type, void *data, int reuse_fd);
 
 /* fs_path_normalize(): Normalize a path to eliminate ., .. and redundant /
 
diff --git a/src/fs/fs.c b/src/fs/fs.c
index 09919e4..5bea0db 100644
--- a/src/fs/fs.c
+++ b/src/fs/fs.c
@@ -42,7 +42,7 @@ void fs_free_descriptor(int fd)
 	fdtable[fd].data = NULL;
 }
 
-int open_generic(fs_descriptor_type_t *type, void *data, int fd)
+int open_generic(fs_descriptor_type_t const *type, void *data, int fd)
 {
 	if(!fdtable) {
 		errno = ENOMEM;
@@ -79,7 +79,7 @@ int open_generic(fs_descriptor_type_t *type, void *data, int fd)
 
 /* Standard streams */
 
-static fs_descriptor_type_t devnull = {
+static fs_descriptor_type_t const devnull = {
 	.read   = NULL,
 	.write  = NULL,
 	.lseek  = NULL,