diff --git a/libc/upstream-openbsd/lib/libc/stdio/open_memstream.c b/libc/upstream-openbsd/lib/libc/stdio/open_memstream.c
index 6ee5a5c27..af0169f67 100644
--- a/libc/upstream-openbsd/lib/libc/stdio/open_memstream.c
+++ b/libc/upstream-openbsd/lib/libc/stdio/open_memstream.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: open_memstream.c,v 1.8 2019/05/02 08:30:10 yasuoka Exp $	*/
+/*	$OpenBSD: open_memstream.c,v 1.10 2023/07/11 12:14:16 claudio Exp $	*/
 
 /*
  * Copyright (c) 2011 Martin Pieuchot <mpi@openbsd.org>
@@ -53,7 +53,6 @@ memstream_write(void *v, const char *b, int l)
 		p = recallocarray(st->string, st->size, sz, 1);
 		if (!p)
 			return (-1);
-		bzero(p + st->size, sz - st->size);
 		*st->pbuf = st->string = p;
 		st->size = sz;
 	}
@@ -136,7 +135,6 @@ open_memstream(char **pbuf, size_t *psize)
 		return (NULL);
 	}
 
-	*st->string = '\0';
 	st->pos = 0;
 	st->len = 0;
 	st->pbuf = pbuf;
diff --git a/libc/upstream-openbsd/lib/libc/stdio/open_wmemstream.c b/libc/upstream-openbsd/lib/libc/stdio/open_wmemstream.c
index aceef3515..fca0b7138 100644
--- a/libc/upstream-openbsd/lib/libc/stdio/open_wmemstream.c
+++ b/libc/upstream-openbsd/lib/libc/stdio/open_wmemstream.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: open_wmemstream.c,v 1.8 2015/09/12 16:23:14 guenther Exp $	*/
+/*	$OpenBSD: open_wmemstream.c,v 1.10 2023/07/11 12:14:16 claudio Exp $	*/
 
 /*
  * Copyright (c) 2011 Martin Pieuchot <mpi@openbsd.org>
@@ -52,10 +52,9 @@ wmemstream_write(void *v, const char *b, int l)
 
 		if (sz < end + 1)
 			sz = end + 1;
-		p = reallocarray(st->string, sz, sizeof(wchar_t));
+		p = recallocarray(st->string, st->size, sz, sizeof(wchar_t));
 		if (!p)
 			return (-1);
-		bzero(p + st->size, (sz - st->size) * sizeof(wchar_t));
 		*st->pbuf = st->string = p;
 		st->size = sz;
 	}
@@ -146,7 +145,6 @@ open_wmemstream(wchar_t **pbuf, size_t *psize)
 		return (NULL);
 	}
 
-	*st->string = L'\0';
 	st->pos = 0;
 	st->len = 0;
 	st->pbuf = pbuf;