diff --git a/src/crypt.c b/src/crypt.c
index daa608a..9f0f68a 100644
--- a/src/crypt.c
+++ b/src/crypt.c
@@ -1267,6 +1267,13 @@
 }
 
 # if defined(FEAT_SODIUM) || defined(PROTO)
+    void
+crypt_sodium_lock_key(char_u *key)
+{
+    if (sodium_init() >= 0)
+	sodium_mlock(key, STRLEN(key));
+}
+
     int
 crypt_sodium_munlock(void *const addr, const size_t len)
 {