diff --git a/files.c b/files.c
index 55cbac857..25ffe9e92 100644
--- a/files.c
+++ b/files.c
@@ -930,6 +930,8 @@ static int open_fdinfos(int pid, struct list_head *list, int state)
 	return ret;
 }
 
+static struct inherit_fd *inherit_fd_lookup_fd(int fd, const char *caller);
+
 int close_old_fds(struct pstree_item *me)
 {
 	DIR *dir;
@@ -1364,7 +1366,7 @@ int inherit_fd_lookup_id(char *id)
 /*
  * Look up the inherit fd list by a file descriptor.
  */
-struct inherit_fd *inherit_fd_lookup_fd(int fd, const char *caller)
+static struct inherit_fd *inherit_fd_lookup_fd(int fd, const char *caller)
 {
 	struct inherit_fd *ret;
 	struct inherit_fd *inh;
diff --git a/include/files.h b/include/files.h
index e3f79cc42..5c9ab4e87 100644
--- a/include/files.h
+++ b/include/files.h
@@ -171,7 +171,6 @@ extern int dump_unsupp_fd(struct fd_parms *p, int lfd,
 extern int inherit_fd_add(char *optarg);
 extern void inherit_fd_log(void);
 extern int inherit_fd_lookup_id(char *id);
-extern struct inherit_fd *inherit_fd_lookup_fd(int fd, const char *caller);
 extern int inherit_fd_resolve_clash(int fd);
 extern int inherit_fd_fini(void);