diff --git a/lib/libc/stdio/vfprintf.c b/lib/libc/stdio/vfprintf.c
index 72178c31aa9..6a1ce394a6c 100644
--- a/lib/libc/stdio/vfprintf.c
+++ b/lib/libc/stdio/vfprintf.c
@@ -294,13 +294,9 @@ vfprintf(FILE * __restrict fp, const char * __restrict fmt0, va_list ap)
 /*
  * The size of the buffer we use as scratch space for integer
  * conversions, among other things.  We need enough space to
- * write a uintmax_t in octal (plus one byte).
+ * write a uintmax_t in binary.
  */
-#if UINTMAX_MAX <= UINT64_MAX
-#define	BUF	32
-#else
-#error "BUF must be large enough to format a uintmax_t"
-#endif
+#define BUF	(sizeof(uintmax_t) * CHAR_BIT)
 
 /*
  * Non-MT-safe version
diff --git a/lib/libc/stdio/vfwprintf.c b/lib/libc/stdio/vfwprintf.c
index b606eec0d9a..67b36643961 100644
--- a/lib/libc/stdio/vfwprintf.c
+++ b/lib/libc/stdio/vfwprintf.c
@@ -374,13 +374,9 @@ vfwprintf(FILE * __restrict fp, const wchar_t * __restrict fmt0, va_list ap)
 /*
  * The size of the buffer we use as scratch space for integer
  * conversions, among other things.  We need enough space to
- * write a uintmax_t in octal (plus one byte).
+ * write a uintmax_t in binary.
  */
-#if UINTMAX_MAX <= UINT64_MAX
-#define	BUF	32
-#else
-#error "BUF must be large enough to format a uintmax_t"
-#endif
+#define BUF	(sizeof(uintmax_t) * CHAR_BIT)
 
 /*
  * Non-MT-safe version