diff --git a/src/buffer.c b/src/buffer.c
index 08db0fc..18aa2a0 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2269,8 +2269,9 @@
 #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));
+    if ((buf->b_p_key != NULL) && (*buf->b_p_key != NUL) &&
+				(crypt_get_method_nr(buf) == CRYPT_M_SOD))
+	crypt_sodium_munlock(buf->b_p_key, STRLEN(buf->b_p_key));
 # endif
     clear_string_option(&buf->b_p_key);
 #endif