diff --git a/libc/stdio/fvwrite.c b/libc/stdio/fvwrite.c
index 57a57e6..39d0604 100644
--- a/libc/stdio/fvwrite.c
+++ b/libc/stdio/fvwrite.c
@@ -48,7 +48,7 @@
 __sfvwrite(FILE *fp, struct __suio *uio)
 {
 	size_t len;
-	char *p;
+	const char *p;
 	struct __siov *iov;
 	int w, s;
 	char *nl;
diff --git a/libc/stdio/fvwrite.h b/libc/stdio/fvwrite.h
index 2344e42..96f65de 100644
--- a/libc/stdio/fvwrite.h
+++ b/libc/stdio/fvwrite.h
@@ -36,7 +36,7 @@
  * I/O descriptors for __sfvwrite().
  */
 struct __siov {
-	void	*iov_base;
+	const void	*iov_base;
 	size_t	iov_len;
 };
 struct __suio {
diff --git a/libc/stdio/vfprintf.c b/libc/stdio/vfprintf.c
index 2ce0361..5a8aa0a 100644
--- a/libc/stdio/vfprintf.c
+++ b/libc/stdio/vfprintf.c
@@ -203,9 +203,9 @@
 	 * below longer.
 	 */
 #define	PADSIZE	16		/* pad chunk size */
-	static char blanks[PADSIZE] =
+	static const char blanks[PADSIZE] =
 	 {' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' '};
-	static char zeroes[PADSIZE] =
+	static const char zeroes[PADSIZE] =
 	 {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'};
 
 	/*