diff --git a/src/proto/crypt.pro b/src/proto/crypt.pro
index d599238..e3ef693 100644
--- a/src/proto/crypt.pro
+++ b/src/proto/crypt.pro
@@ -26,6 +26,7 @@
 void crypt_check_current_method(void);
 char_u *crypt_get_key(int store, int twice);
 void crypt_append_msg(buf_T *buf);
+void crypt_sodium_lock_key(char_u *key);
 int crypt_sodium_munlock(void *const addr, const size_t len);
 void crypt_sodium_randombytes_buf(void *const buf, const size_t size);
 int crypt_sodium_init(void);