diff --git a/src/memline.c b/src/memline.c
index c5b22e0924bbf77a92de9c365b4bba4336ba45ae..06b30cf7289b66ca5b7377eeb62f4a25541221c2 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -4923,7 +4923,7 @@ ml_crypt_prepare(mfp, offset, reading)
 	/* Using blowfish, add salt and seed. We use the byte offset of the
 	 * block for the salt. */
 	vim_snprintf((char *)salt, sizeof(salt), "%ld", (long)offset);
-	bf_key_init(key, salt, STRLEN(salt));
+	bf_key_init(key, salt, (int)STRLEN(salt));
 	bf_ofb_init(seed, MF_SEED_LEN);
     }
 }