diff --git a/libc/fmt/ntoa.c b/libc/fmt/ntoa.c
index 2c047812f..bce92a582 100644
--- a/libc/fmt/ntoa.c
+++ b/libc/fmt/ntoa.c
@@ -32,43 +32,66 @@ static int __fmt_ntoa_format(int out(const char *, void *, size_t), void *arg,
                              char *buf, unsigned len, bool negative,
                              unsigned log2base, unsigned prec, unsigned width,
                              unsigned char flags, const char *alphabet) {
-  unsigned i;
+  unsigned i, prec_width_zeros;
+  char alternate_form_middle_char, sign_character;
+  unsigned actual_buf_len;
+  actual_buf_len = len;
+  prec_width_zeros = 0;
   /* pad leading zeros */
   if (width && (flags & FLAGS_ZEROPAD) &&
       (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
     width--;
   }
-  while ((len < prec) && (len < BUFFER_SIZE)) {
-    buf[len++] = '0';
+  if (len < prec) {
+    prec_width_zeros += (prec - len);
+    len = prec;
   }
-  while ((flags & FLAGS_ZEROPAD) && (len < width) && (len < BUFFER_SIZE)) {
-    buf[len++] = '0';
+  if ((flags & FLAGS_ZEROPAD) && (len < width)) {
+    prec_width_zeros += (width - len);
+    len = width;
   }
   /* handle hash */
   if (flags & FLAGS_HASH) {
     if ((!(flags & FLAGS_PRECISION) || log2base == 3) && len &&
-        ((len >= prec) || (len >= width)) && buf[len - 1] == '0') {
-      len--;
-      if (len && (log2base == 4 || log2base == 1) && buf[len - 1] == '0') {
-        len--;
+        ((len >= prec) || (len >= width)) &&
+        (prec_width_zeros || buf[len - 1] == '0')) {
+      if (prec_width_zeros) {
+        --prec_width_zeros;
+      }
+      --len;
+      if (len < actual_buf_len) {
+        actual_buf_len = len;
+      }
+      if (len && (log2base == 4 || log2base == 1) &&
+          (prec_width_zeros || buf[len - 1] == '0')) {
+        if (prec_width_zeros) {
+          --prec_width_zeros;
+        }
+        --len;
+        if (len < actual_buf_len) {
+          actual_buf_len = len;
+        }
       }
     }
-    if ((log2base == 4 || log2base == 1) && len < BUFFER_SIZE) {
-      buf[len++] = alphabet[17];  // x, X or b (for the corresponding conversion
-                                  // specifiers)
-    }
-    if (len < BUFFER_SIZE) {
-      buf[len++] = '0';
+    alternate_form_middle_char = '\0';
+    if ((log2base == 4 || log2base == 1)) {
+      ++len;
+      alternate_form_middle_char =
+          alphabet[17];  // x, X or b (for the corresponding conversion
+                         // specifiers)
     }
+    ++len;
   }
-  if (len < BUFFER_SIZE) {
-    if (negative) {
-      buf[len++] = '-';
-    } else if (flags & FLAGS_PLUS) {
-      buf[len++] = '+'; /* ignore the space if the '+' exists */
-    } else if (flags & FLAGS_SPACE) {
-      buf[len++] = ' ';
-    }
+  sign_character = '\0';
+  if (negative) {
+    ++len;
+    sign_character = '-';
+  } else if (flags & FLAGS_PLUS) {
+    ++len;
+    sign_character = '+'; /* ignore the space if the '+' exists */
+  } else if (flags & FLAGS_SPACE) {
+    ++len;
+    sign_character = ' ';
   }
   /* pad spaces up to given width */
   if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
@@ -76,8 +99,17 @@ static int __fmt_ntoa_format(int out(const char *, void *, size_t), void *arg,
       if (__fmt_pad(out, arg, width - len) == -1) return -1;
     }
   }
-  reverse(buf, len);
-  if (out(buf, arg, len) == -1) return -1;
+  if (sign_character != '\0' && out(&sign_character, arg, 1) == -1) return -1;
+  if (flags & FLAGS_HASH) {
+    if (out("0", arg, 1) == -1) return -1;
+    if (alternate_form_middle_char != '\0' &&
+        out(&alternate_form_middle_char, arg, 1) == -1)
+      return -1;
+  }
+  for (i = 0; i < prec_width_zeros; ++i)
+    if (out("0", arg, 1) == -1) return -1;
+  reverse(buf, actual_buf_len);
+  if (out(buf, arg, actual_buf_len) == -1) return -1;
   /* append pad spaces up to given width */
   if (flags & FLAGS_LEFT) {
     if (len < width) {
@@ -94,9 +126,9 @@ int __fmt_ntoa2(int out(const char *, void *, size_t), void *arg,
   unsigned len, count, digit;
   char buf[BUFFER_SIZE];
   len = 0;
-  /* we check for log2base != 3 because otherwise we'll print nothing for a value of 0 with precision 0 when # mandates that one be printed */
-  if (!value && log2base != 3)
-    flags &= ~FLAGS_HASH;
+  /* we check for log2base != 3 because otherwise we'll print nothing for a
+   * value of 0 with precision 0 when # mandates that one be printed */
+  if (!value && log2base != 3) flags &= ~FLAGS_HASH;
   if (value || !(flags & FLAGS_PRECISION)) {
     count = 0;
     do {
diff --git a/test/libc/fmt/fmt_test.c b/test/libc/fmt/fmt_test.c
index 840599913..dc3a51489 100644
--- a/test/libc/fmt/fmt_test.c
+++ b/test/libc/fmt/fmt_test.c
@@ -105,10 +105,16 @@ TEST(fmt, o) {
   EXPECT_STREQ("0001777777777777777777634", _gc(xasprintf("%#.25lo", -100L)));
   EXPECT_STREQ("0001777777777777777777634", _gc(xasprintf("%#.25llo", -100LL)));
   EXPECT_STREQ("0", _gc(xasprintf("%#.o", 0)));
+  EXPECT_STREQ("  056520", _gc(xasprintf("%#8.6o", 23888)));
+  EXPECT_STREQ("00144   ", _gc(xasprintf("%#-8.5llo", 100ll)));
+  EXPECT_STREQ("0 ", _gc(xasprintf("%-#02lo", 0l)));
+  EXPECT_STREQ("0", _gc(xasprintf("%#01lo", 0l)));
+  EXPECT_STREQ("00", _gc(xasprintf("%#02lo", 0l)));
 }
 
 TEST(fmt, b) {
   EXPECT_STREQ("000010100     ", _gc(xasprintf("%-14.9b", 20)));
+  EXPECT_STREQ("0b110", _gc(xasprintf("%#b", 6)));
 }
 
 TEST(fmt, s) {
diff --git a/test/libc/fmt/snprintf_test.c b/test/libc/fmt/snprintf_test.c
new file mode 100644
index 000000000..aaaf7cb01
--- /dev/null
+++ b/test/libc/fmt/snprintf_test.c
@@ -0,0 +1,29 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2023 Gabriel Ravier                                                │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/fmt/fmt.h"
+#include "libc/str/str.h"
+#include "libc/testlib/testlib.h"
+
+TEST(snprintf, testVeryLargePrecision) {
+  char buf[512] = {};
+  int i = snprintf(buf, sizeof(buf), "%.9999u", 10);
+
+  ASSERT_EQ(i, 9999);
+  ASSERT_EQ(strlen(buf), 511);
+}