diff --git a/src/buffer.c b/src/buffer.c
index 59397e4..628c82f 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2306,6 +2306,10 @@
     clear_string_option(&buf->b_p_fex);
 #endif
 #ifdef FEAT_CRYPT
+# ifdef FEAT_SODIUM
+    if (buf->b_p_key != NULL && (crypt_get_method_nr(buf) == CRYPT_M_SOD))
+	sodium_munlock(buf->b_p_key, STRLEN(buf->b_p_key));
+# endif
     clear_string_option(&buf->b_p_key);
 #endif
     clear_string_option(&buf->b_p_kp);