diff --git a/libc/stdio/scanf_common.h b/libc/stdio/scanf_common.h
new file mode 100644
index 0000000..8132e90
--- /dev/null
+++ b/libc/stdio/scanf_common.h
@@ -0,0 +1,115 @@
+/*	$OpenBSD: vfscanf.c,v 1.31 2014/03/19 05:17:01 guenther Exp $ */
+/*-
+ * Copyright (c) 1990, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ctype.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <locale.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/param.h>
+#include <wctype.h>
+#include "local.h"
+
+#include <platform/bionic/macros.h>
+#include <private/bionic_fortify.h>
+#include <private/bionic_mbstate.h>
+
+#define BUF 513 /* Maximum length of numeric string. */
+
+// Flags used during conversion.
+// Size/type:
+#define LONG 0x00001        // l: long or double
+#define LONGDBL 0x00002     // L: long double
+#define SHORT 0x00004       // h: short
+#define SHORTSHORT 0x00008  // hh: 8 bit integer
+#define LLONG 0x00010       // ll: long long (+ deprecated q: quad)
+#define POINTER 0x00020     // p: void* (as hex)
+#define SIZEINT 0x00040     // z: (signed) size_t
+#define MAXINT 0x00080      // j: intmax_t
+#define PTRINT 0x00100      // t: ptrdiff_t
+#define NOSKIP 0x00200      // [ or c: do not skip blanks
+// Modifiers:
+#define SUPPRESS 0x00400  // *: suppress assignment
+#define UNSIGNED 0x00800  // %[oupxX] conversions
+#define ALLOCATE 0x01000  // m: allocate a char*
+// Internal use during integer parsing:
+#define SIGNOK 0x02000    // +/- is (still) legal
+#define HAVESIGN 0x04000  // Sign detected
+#define NDIGITS 0x08000   // No digits detected
+#define PFXOK 0x10000     // "0x" prefix is (still) legal
+#define PFBOK 0x20000     // "0b" prefix is (still) legal
+#define NZDIGITS 0x40000  // No zero digits detected
+
+// Conversion types.
+#define CT_CHAR 0    // %c conversion
+#define CT_CCL 1     // %[...] conversion
+#define CT_STRING 2  // %s conversion
+#define CT_INT 3     // Integer: strtoimax/strtoumax
+#define CT_FLOAT 4   // Float: strtod
+
+#define to_digit(c) static_cast<int>((c) - '0')
+#define is_digit(c) ((unsigned)to_digit(c) <= 9)
+
+// Append a digit to a value and check for overflow.
+#define APPEND_DIGIT(val, dig)               \
+  do {                                       \
+    if ((val) > INT_MAX / 10)                \
+      errno = ENOMEM;                        \
+    else {                                   \
+      (val) *= 10;                           \
+      if ((val) > INT_MAX - to_digit((dig))) \
+        errno = ENOMEM;                      \
+      else                                   \
+        (val) += to_digit((dig));            \
+    }                                        \
+  } while (0)
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-function"
+// Trasnlate a fixed size integer argument for the %w/%wf format to a
+// flag representation. Supported sizes are 8, 16, 32, and 64 so far.
+// See details in bionic/libc/include/stdint.h
+static int w_to_flag(int size, bool fast) {
+  static constexpr int fast_size = sizeof(void*) == 8 ? LLONG : 0;
+  if (size == 8) return SHORTSHORT;
+  if (size == 16) return fast ? fast_size : SHORT;
+  if (size == 32) return fast ? fast_size : 0;
+  if (size == 64) return LLONG;
+  __fortify_fatal("%%w%s%d is unsupported", fast ? "f" : "", size);
+}
+
+#pragma clang diagnostic pop
\ No newline at end of file
diff --git a/libc/stdio/vfscanf.cpp b/libc/stdio/vfscanf.cpp
index dfd001d..65f54a5 100644
--- a/libc/stdio/vfscanf.cpp
+++ b/libc/stdio/vfscanf.cpp
@@ -31,53 +31,7 @@
  * SUCH DAMAGE.
  */
 
-#include <ctype.h>
-#include <inttypes.h>
-#include <stdarg.h>
-#include <stddef.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/param.h>
-#include <wctype.h>
-#include "local.h"
-
-#include <private/bionic_fortify.h>
-#include <platform/bionic/macros.h>
-#include <private/bionic_mbstate.h>
-
-#define BUF 513 /* Maximum length of numeric string. */
-
-// Flags used during conversion.
-// Size/type:
-#define LONG       0x00001 // l: long or double
-#define LONGDBL    0x00002 // L: long double
-#define SHORT      0x00004 // h: short
-#define SHORTSHORT 0x00008 // hh: 8 bit integer
-#define LLONG      0x00010 // ll: long long (+ deprecated q: quad)
-#define POINTER    0x00020 // p: void* (as hex)
-#define SIZEINT    0x00040 // z: (signed) size_t
-#define MAXINT     0x00080 // j: intmax_t
-#define PTRINT     0x00100 // t: ptrdiff_t
-#define NOSKIP     0x00200 // [ or c: do not skip blanks
-// Modifiers:
-#define SUPPRESS   0x00400 // *: suppress assignment
-#define UNSIGNED   0x00800 // %[oupxX] conversions
-#define ALLOCATE   0x01000 // m: allocate a char*
-// Internal use during integer parsing:
-#define SIGNOK     0x02000 // +/- is (still) legal
-#define HAVESIGN   0x04000 // Sign detected
-#define NDIGITS    0x08000 // No digits detected
-#define PFXOK      0x10000 // "0x" prefix is (still) legal
-#define PFBOK      0x20000 // "0b" prefix is (still) legal
-#define NZDIGITS   0x40000 // No zero digits detected
-
-// Conversion types.
-#define CT_CHAR 0   // %c conversion
-#define CT_CCL 1    // %[...] conversion
-#define CT_STRING 2 // %s conversion
-#define CT_INT 3    // Integer: strtoimax/strtoumax
-#define CT_FLOAT 4  // Float: strtod
+#include "scanf_common.h"
 
 static const unsigned char* __sccl(char*, const unsigned char*);
 
@@ -122,6 +76,7 @@
      */
 again:
     c = *fmt++;
+reswitch:
     switch (c) {
       case '%':
 literal:
@@ -220,6 +175,18 @@
         base = 10;
         break;
 
+      case 'w': {
+        int size = 0;
+        bool fast = false;
+        c = *fmt++;
+        while (is_digit(c)) {
+          APPEND_DIGIT(size, c);
+          c = *fmt++;
+        }
+        flags |= w_to_flag(size, fast);
+        goto reswitch;
+      }
+
       case 'X':
       case 'x':
         flags |= PFXOK; /* enable 0x prefixing */
diff --git a/libc/stdio/vfwscanf.cpp b/libc/stdio/vfwscanf.cpp
index 5f21acd..14b1754 100644
--- a/libc/stdio/vfwscanf.cpp
+++ b/libc/stdio/vfwscanf.cpp
@@ -31,62 +31,7 @@
  * SUCH DAMAGE.
  */
 
-#include <inttypes.h>
-#include <limits.h>
-#include <locale.h>
-#include <stdarg.h>
-#include <stddef.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <wctype.h>
-#include "local.h"
-
-#include <platform/bionic/macros.h>
-
-#define BUF 513 /* Maximum length of numeric string. */
-
-/*
- * Flags used during conversion.
- */
-#define LONG 0x00001       /* l: long or double */
-#define LONGDBL 0x00002    /* L: long double */
-#define SHORT 0x00004      /* h: short */
-#define SHORTSHORT 0x00008 /* hh: 8 bit integer */
-#define LLONG 0x00010      /* ll: long long (+ deprecated q: quad) */
-#define POINTER 0x00020    /* p: void * (as hex) */
-#define SIZEINT 0x00040    /* z: (signed) size_t */
-#define MAXINT 0x00080     /* j: intmax_t */
-#define PTRINT 0x00100     /* t: ptrdiff_t */
-#define NOSKIP 0x00200     /* [ or c: do not skip blanks */
-#define SUPPRESS 0x00400   /* *: suppress assignment */
-#define UNSIGNED 0x00800   /* %[oupxX] conversions */
-
-/*
- * The following are used in numeric conversions only:
- * SIGNOK, HAVESIGN, NDIGITS, DPTOK, and EXPOK are for floating point;
- * SIGNOK, HAVESIGN, NDIGITS, PFXOK, and NZDIGITS are for integral.
- */
-#define SIGNOK   0x01000  /* +/- is (still) legal */
-#define HAVESIGN 0x02000 /* sign detected */
-#define NDIGITS  0x04000 /* no digits detected */
-
-#define DPTOK    0x08000 /* (float) decimal point is still legal */
-#define EXPOK    0x10000 /* (float) exponent (e+3, etc) still legal */
-
-#define PFBOK    0x20000 /* 0x prefix is (still) legal */
-#define PFXOK    0x40000 /* 0x prefix is (still) legal */
-#define NZDIGITS 0x80000 /* no zero digits detected */
-
-/*
- * Conversion types.
- */
-#define CT_CHAR 0   /* %c conversion */
-#define CT_CCL 1    /* %[...] conversion */
-#define CT_STRING 2 /* %s conversion */
-#define CT_INT 3    /* integer, i.e., strtoimax or strtoumax */
-#define CT_FLOAT 4  /* floating, i.e., strtod */
-
+#include "scanf_common.h"
 // An interpretive version of __sccl from vfscanf.c --- a table of all wchar_t values would
 // be a little too expensive, and some kind of compressed version isn't worth the trouble.
 static inline bool in_ccl(wchar_t wc, const wchar_t* ccl) {
@@ -176,6 +121,7 @@
      */
   again:
     c = *fmt++;
+  reswitch:
     switch (c) {
       case '%':
       literal:
@@ -273,6 +219,18 @@
         base = 10;
         break;
 
+      case 'w': {
+        int size = 0;
+        bool fast = false;
+        c = *fmt++;
+        while (is_digit(c)) {
+          APPEND_DIGIT(size, c);
+          c = *fmt++;
+        }
+        flags |= w_to_flag(size, fast);
+        goto reswitch;
+      }
+
       case 'X':
       case 'x':
         flags |= PFXOK; /* enable 0x prefixing */