diff --git a/ChangeLog b/ChangeLog
index d2a1888554..d8cbbcc623 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,29 @@
+2018-12-05  Zack Weinberg  <zackw@panix.com>
+	    Gabriel F. T. Gomes  <gabriel@inconstante.eti.br>
+
+	* stdio-common/isoc99_scanf.c
+	* stdio-common/isoc99_fscanf.c
+	* stdio-common/isoc99_sscanf.c
+	* stdio-common/isoc99_vscanf.c
+	* stdio-common/isoc99_vfscanf.c
+	* stdio-common/isoc99_vsscanf.c
+	* wcsmbs/isoc99_wscanf.c
+	* wcsmbs/isoc99_fwscanf.c
+	* wcsmbs/isoc99_swscanf.c
+	* wcsmbs/isoc99_vwscanf.c
+	* wcsmbs/isoc99_vfwscanf.c
+	* wcsmbs/isoc99_vswscanf.c:
+	Pass SCANF_ISOC99_A to __vfscanf_internal and/or __vfwscanf_internal.
+	Do not set _IO_FLAGS2_SCANF_STD on the FILE passed to that function.
+	No need to lock and unlock the FILE passed to that function.
+
+	* stdio-common/vfscanf-internal.c
+	(__vfscanf_internal, __vfwscanf_internal):
+	Don't look at _IO_FLAGS2_SCANF_STD.
+	* libio/libioP.h (_IO_acquire_lock_clear_flags2_fct)
+	(_IO_release_lock): Don't clear _IO_FLAGS2_SCANF_STD.
+	* libio/libio.h (_IO_FLAGS2_SCANF_STD): Delete.
+
 2018-12-05  Zack Weinberg  <zackw@panix.com>
 	    Gabriel F. T. Gomes  <gabriel@inconstante.eti.br>
 
diff --git a/libio/libio.h b/libio/libio.h
index d4eba2df54..30cb7d784f 100644
--- a/libio/libio.h
+++ b/libio/libio.h
@@ -92,7 +92,6 @@ typedef union
 #define _IO_FLAGS2_NOTCANCEL 2
 #define _IO_FLAGS2_FORTIFY 4
 #define _IO_FLAGS2_USER_WBUF 8
-#define _IO_FLAGS2_SCANF_STD 16
 #define _IO_FLAGS2_NOCLOSE 32
 #define _IO_FLAGS2_CLOEXEC 64
 #define _IO_FLAGS2_NEED_LOCK 128
diff --git a/libio/libioP.h b/libio/libioP.h
index 525dce19ee..9e971cb96b 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -786,7 +786,7 @@ __attribute__ ((__always_inline__))
 _IO_acquire_lock_clear_flags2_fct (FILE **p)
 {
   FILE *fp = *p;
-  fp->_flags2 &= ~(_IO_FLAGS2_FORTIFY | _IO_FLAGS2_SCANF_STD);
+  fp->_flags2 &= ~(_IO_FLAGS2_FORTIFY);
   if ((fp->_flags & _IO_USER_LOCK) == 0)
     _IO_funlockfile (fp);
 }
@@ -800,8 +800,7 @@ _IO_acquire_lock_clear_flags2_fct (FILE **p)
     FILE *_IO_acquire_lock_file = (_fp)
 # define _IO_release_lock(_fp)						      \
     if (_IO_acquire_lock_file != NULL)					      \
-      _IO_acquire_lock_file->_flags2 &= ~(_IO_FLAGS2_FORTIFY		      \
-                                          | _IO_FLAGS2_SCANF_STD);	      \
+      _IO_acquire_lock_file->_flags2 &= ~(_IO_FLAGS2_FORTIFY);		      \
   } while (0)
 #endif
 
diff --git a/stdio-common/isoc99_fscanf.c b/stdio-common/isoc99_fscanf.c
index 4210d11f2b..d7b5993f3e 100644
--- a/stdio-common/isoc99_fscanf.c
+++ b/stdio-common/isoc99_fscanf.c
@@ -20,20 +20,15 @@
 #include <stdio.h>
 
 /* Read formatted input from STREAM according to the format string FORMAT.  */
-/* VARARGS2 */
 int
 __isoc99_fscanf (FILE *stream, const char *format, ...)
 {
   va_list arg;
   int done;
 
-  _IO_acquire_lock_clear_flags2 (stream);
-  stream->_flags2 |= _IO_FLAGS2_SCANF_STD;
-
   va_start (arg, format);
-  done = __vfscanf_internal (stream, format, arg, 0);
+  done = __vfscanf_internal (stream, format, arg, SCANF_ISOC99_A);
   va_end (arg);
 
-  _IO_release_lock (stream);
   return done;
 }
diff --git a/stdio-common/isoc99_scanf.c b/stdio-common/isoc99_scanf.c
index 64c873eed9..3998322ea1 100644
--- a/stdio-common/isoc99_scanf.c
+++ b/stdio-common/isoc99_scanf.c
@@ -19,26 +19,16 @@
 #include <stdio.h>
 #include <libioP.h>
 
-
 /* Read formatted input from stdin according to the format string FORMAT.  */
-/* VARARGS1 */
 int
 __isoc99_scanf (const char *format, ...)
 {
   va_list arg;
   int done;
 
-#ifdef _IO_MTSAFE_IO
-  _IO_acquire_lock_clear_flags2 (stdin);
-#endif
-  stdin->_flags2 |= _IO_FLAGS2_SCANF_STD;
-
   va_start (arg, format);
-  done = __vfscanf_internal (stdin, format, arg, 0);
+  done = __vfscanf_internal (stdin, format, arg, SCANF_ISOC99_A);
   va_end (arg);
 
-#ifdef _IO_MTSAFE_IO
-  _IO_release_lock (stdin);
-#endif
   return done;
 }
diff --git a/stdio-common/isoc99_sscanf.c b/stdio-common/isoc99_sscanf.c
index 2c89a03fe9..c9e5103b81 100644
--- a/stdio-common/isoc99_sscanf.c
+++ b/stdio-common/isoc99_sscanf.c
@@ -26,10 +26,9 @@ __isoc99_sscanf (const char *s, const char *format, ...)
   int done;
   _IO_strfile sf;
   FILE *f = _IO_strfile_read (&sf, s);
-  f->_flags2 |= _IO_FLAGS2_SCANF_STD;
 
   va_start (arg, format);
-  done = __vfscanf_internal (f, format, arg, 0);
+  done = __vfscanf_internal (f, format, arg, SCANF_ISOC99_A);
   va_end (arg);
 
   return done;
diff --git a/stdio-common/isoc99_vfscanf.c b/stdio-common/isoc99_vfscanf.c
index c96ca831ae..3c59c60b3e 100644
--- a/stdio-common/isoc99_vfscanf.c
+++ b/stdio-common/isoc99_vfscanf.c
@@ -19,16 +19,9 @@
 #include <stdio.h>
 
 /* Read formatted input from STREAM according to the format string FORMAT.  */
-/* VARARGS2 */
 int
 __isoc99_vfscanf (FILE *stream, const char *format, va_list args)
 {
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (stream);
-  stream->_flags2 |= _IO_FLAGS2_SCANF_STD;
-  done = __vfscanf_internal (stream, format, args, 0);
-  _IO_release_lock (stream);
-  return done;
+  return __vfscanf_internal (stream, format, args, SCANF_ISOC99_A);
 }
 libc_hidden_def (__isoc99_vfscanf)
diff --git a/stdio-common/isoc99_vscanf.c b/stdio-common/isoc99_vscanf.c
index 72ae72ddee..fc5d609ae7 100644
--- a/stdio-common/isoc99_vscanf.c
+++ b/stdio-common/isoc99_vscanf.c
@@ -19,15 +19,8 @@
 #include <stdio.h>
 
 /* Read formatted input from STDIN according to the format string FORMAT.  */
-/* VARARGS2 */
 int
 __isoc99_vscanf (const char *format, va_list args)
 {
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (stdin);
-  stdin->_flags2 |= _IO_FLAGS2_SCANF_STD;
-  done = __vfscanf_internal (stdin, format, args, 0);
-  _IO_release_lock (stdin);
-  return done;
+  return __vfscanf_internal (stdin, format, args, SCANF_ISOC99_A);
 }
diff --git a/stdio-common/isoc99_vsscanf.c b/stdio-common/isoc99_vsscanf.c
index 02bc0f50e6..dfc394bb51 100644
--- a/stdio-common/isoc99_vsscanf.c
+++ b/stdio-common/isoc99_vsscanf.c
@@ -31,7 +31,6 @@ __isoc99_vsscanf (const char *string, const char *format, va_list args)
 {
   _IO_strfile sf;
   FILE *f = _IO_strfile_read (&sf, string);
-  f->_flags2 |= _IO_FLAGS2_SCANF_STD;
-  return __vfscanf_internal (f, format, args, 0);
+  return __vfscanf_internal (f, format, args, SCANF_ISOC99_A);
 }
 libc_hidden_def (__isoc99_vsscanf)
diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c
index 6bd0138f66..df79d91eda 100644
--- a/stdio-common/vfscanf-internal.c
+++ b/stdio-common/vfscanf-internal.c
@@ -335,8 +335,6 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
   /* Temporarily honor the environmental mode bits.  */
   if (__ldbl_is_dbl)
     mode_flags |= SCANF_LDBL_IS_DBL;
-  if (s->_flags2 & _IO_FLAGS2_SCANF_STD)
-    mode_flags |= SCANF_ISOC99_A;
 
 #ifdef __va_copy
   __va_copy (arg, argptr);
diff --git a/wcsmbs/isoc99_fwscanf.c b/wcsmbs/isoc99_fwscanf.c
index 00b07dd48e..5829607916 100644
--- a/wcsmbs/isoc99_fwscanf.c
+++ b/wcsmbs/isoc99_fwscanf.c
@@ -21,20 +21,15 @@
 #include <wchar.h>
 
 /* Read formatted input from STREAM according to the format string FORMAT.  */
-/* VARARGS2 */
 int
 __isoc99_fwscanf (FILE *stream, const wchar_t *format, ...)
 {
   va_list arg;
   int done;
 
-  _IO_acquire_lock_clear_flags2 (stream);
-  stream->_flags2 |= _IO_FLAGS2_SCANF_STD;
-
   va_start (arg, format);
-  done = __vfwscanf_internal (stream, format, arg, 0);
+  done = __vfwscanf_internal (stream, format, arg, SCANF_ISOC99_A);
   va_end (arg);
 
-  _IO_release_lock (stream);
   return done;
 }
diff --git a/wcsmbs/isoc99_swscanf.c b/wcsmbs/isoc99_swscanf.c
index 40401d0aa1..f90e56d97f 100644
--- a/wcsmbs/isoc99_swscanf.c
+++ b/wcsmbs/isoc99_swscanf.c
@@ -28,10 +28,9 @@ __isoc99_swscanf (const wchar_t *s, const wchar_t *format, ...)
   _IO_strfile sf;
   struct _IO_wide_data wd;
   FILE *f = _IO_strfile_readw (&sf, &wd, s);
-  f->_flags2 |= _IO_FLAGS2_SCANF_STD;
 
   va_start (arg, format);
-  done = __vfwscanf_internal (f, format, arg, 0);
+  done = __vfwscanf_internal (f, format, arg, SCANF_ISOC99_A);
   va_end (arg);
 
   return done;
diff --git a/wcsmbs/isoc99_vfwscanf.c b/wcsmbs/isoc99_vfwscanf.c
index f70c6b596d..715d354b5a 100644
--- a/wcsmbs/isoc99_vfwscanf.c
+++ b/wcsmbs/isoc99_vfwscanf.c
@@ -20,16 +20,9 @@
 #include <wchar.h>
 
 /* Read formatted input from STREAM according to the format string FORMAT.  */
-/* VARARGS2 */
 int
 __isoc99_vfwscanf (FILE *stream, const wchar_t *format, va_list args)
 {
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (stream);
-  stream->_flags2 |= _IO_FLAGS2_SCANF_STD;
-  done = __vfwscanf_internal (stream, format, args, 0);
-  _IO_release_lock (stream);
-  return done;
+  return __vfwscanf_internal (stream, format, args, SCANF_ISOC99_A);
 }
 libc_hidden_def (__isoc99_vfwscanf)
diff --git a/wcsmbs/isoc99_vswscanf.c b/wcsmbs/isoc99_vswscanf.c
index b91eb651a3..0d8ef7611a 100644
--- a/wcsmbs/isoc99_vswscanf.c
+++ b/wcsmbs/isoc99_vswscanf.c
@@ -33,7 +33,6 @@ __isoc99_vswscanf (const wchar_t *string, const wchar_t *format, va_list args)
   _IO_strfile sf;
   struct _IO_wide_data wd;
   FILE *f = _IO_strfile_readw (&sf, &wd, string);
-  f->_flags2 |= _IO_FLAGS2_SCANF_STD;
-  return __vfwscanf_internal (f, format, args, 0);
+  return __vfwscanf_internal (f, format, args, SCANF_ISOC99_A);
 }
 libc_hidden_def (__isoc99_vswscanf)
diff --git a/wcsmbs/isoc99_vwscanf.c b/wcsmbs/isoc99_vwscanf.c
index eb22c8acae..3ac3182608 100644
--- a/wcsmbs/isoc99_vwscanf.c
+++ b/wcsmbs/isoc99_vwscanf.c
@@ -20,15 +20,8 @@
 #include <wchar.h>
 
 /* Read formatted input from STDIN according to the format string FORMAT.  */
-/* VARARGS2 */
 int
 __isoc99_vwscanf (const wchar_t *format, va_list args)
 {
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (stdin);
-  stdin->_flags2 |= _IO_FLAGS2_SCANF_STD;
-  done = __vfwscanf_internal (stdin, format, args, 0);
-  _IO_release_lock (stdin);
-  return done;
+  return __vfwscanf_internal (stdin, format, args, SCANF_ISOC99_A);
 }
diff --git a/wcsmbs/isoc99_wscanf.c b/wcsmbs/isoc99_wscanf.c
index 59f80d78fb..b9418f7912 100644
--- a/wcsmbs/isoc99_wscanf.c
+++ b/wcsmbs/isoc99_wscanf.c
@@ -22,20 +22,15 @@
 
 
 /* Read formatted input from stdin according to the format string FORMAT.  */
-/* VARARGS1 */
 int
 __isoc99_wscanf (const wchar_t *format, ...)
 {
   va_list arg;
   int done;
 
-  _IO_acquire_lock_clear_flags2 (stdin);
-  stdin->_flags2 |= _IO_FLAGS2_SCANF_STD;
-
   va_start (arg, format);
-  done = __vfwscanf_internal (stdin, format, arg, 0);
+  done = __vfwscanf_internal (stdin, format, arg, SCANF_ISOC99_A);
   va_end (arg);
 
-  _IO_release_lock (stdin);
   return done;
 }