diff --git a/ChangeLog b/ChangeLog
index bf038e7c..2f90c42f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2009-12-05  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
+
+	In configure script, if --with-PACKAGE and --enable-FEATURE are
+	given and PACKAGE is missing in the system or FEATURE cannot be
+	enabled, print error message and stop the script.
+	* configure.ac
+	* m4/aria2_arg.m4
+
 2009-12-04  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
 
 	Halt metadata download immediately when metadata download is done.
diff --git a/configure b/configure
index 666c9608..fee34a48 100755
--- a/configure
+++ b/configure
@@ -3583,7 +3583,7 @@ _ACEOF
 
 # Check whether --with-gnutls was given.
 if test "${with_gnutls+set}" = set; then :
-  withval=$with_gnutls; with_gnutls=$withval
+  withval=$with_gnutls; with_gnutls_requested=$withval with_gnutls=$withval
 else
   with_gnutls=yes
 fi
@@ -3592,7 +3592,7 @@ fi
 
 # Check whether --with-openssl was given.
 if test "${with_openssl+set}" = set; then :
-  withval=$with_openssl; with_openssl=$withval
+  withval=$with_openssl; with_openssl_requested=$withval with_openssl=$withval
 else
   with_openssl=yes
 fi
@@ -3601,7 +3601,7 @@ fi
 
 # Check whether --with-sqlite3 was given.
 if test "${with_sqlite3+set}" = set; then :
-  withval=$with_sqlite3; with_sqlite3=$withval
+  withval=$with_sqlite3; with_sqlite3_requested=$withval with_sqlite3=$withval
 else
   with_sqlite3=yes
 fi
@@ -3610,7 +3610,7 @@ fi
 
 # Check whether --with-libxml2 was given.
 if test "${with_libxml2+set}" = set; then :
-  withval=$with_libxml2; with_libxml2=$withval
+  withval=$with_libxml2; with_libxml2_requested=$withval with_libxml2=$withval
 else
   with_libxml2=yes
 fi
@@ -3619,7 +3619,7 @@ fi
 
 # Check whether --with-libexpat was given.
 if test "${with_libexpat+set}" = set; then :
-  withval=$with_libexpat; with_libexpat=$withval
+  withval=$with_libexpat; with_libexpat_requested=$withval with_libexpat=$withval
 else
   with_libexpat=yes
 fi
@@ -3628,7 +3628,7 @@ fi
 
 # Check whether --with-libcares was given.
 if test "${with_libcares+set}" = set; then :
-  withval=$with_libcares; with_libcares=$withval
+  withval=$with_libcares; with_libcares_requested=$withval with_libcares=$withval
 else
   with_libcares=yes
 fi
@@ -3637,7 +3637,7 @@ fi
 
 # Check whether --with-libz was given.
 if test "${with_libz+set}" = set; then :
-  withval=$with_libz; with_libz=$withval
+  withval=$with_libz; with_libz_requested=$withval with_libz=$withval
 else
   with_libz=yes
 fi
@@ -3646,7 +3646,7 @@ fi
 
 # Check whether --enable-bittorrent was given.
 if test "${enable_bittorrent+set}" = set; then :
-  enableval=$enable_bittorrent; enable_bittorrent=$enableval
+  enableval=$enable_bittorrent; enable_bittorrent_requested=$enableval enable_bittorrent=$enableval
 else
   enable_bittorrent=yes
 fi
@@ -3654,7 +3654,7 @@ fi
 
 # Check whether --enable-metalink was given.
 if test "${enable_metalink+set}" = set; then :
-  enableval=$enable_metalink; enable_metalink=$enableval
+  enableval=$enable_metalink; enable_metalink_requested=$enableval enable_metalink=$enableval
 else
   enable_metalink=yes
 fi
@@ -3662,7 +3662,7 @@ fi
 
 # Check whether --enable-epoll was given.
 if test "${enable_epoll+set}" = set; then :
-  enableval=$enable_epoll; enable_epoll=$enableval
+  enableval=$enable_epoll; enable_epoll_requested=$enableval enable_epoll=$enableval
 else
   enable_epoll=yes
 fi
@@ -5889,6 +5889,11 @@ rm -f core conftest.err conftest.$ac_objext \
 
 $as_echo "#define HAVE_LIBXML2 1" >>confdefs.h
 
+  elif test "x$with_libxml2_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "libxml2 is requested but not found in the system.
+See \`config.log' for more details." "$LINENO" 5; }
   fi
 fi
 
@@ -5970,6 +5975,13 @@ LIBS=$LIBS_save
 CPPFLAGS=$CPPFLAGS_save
 
 
+  if test "x$have_libexpat" != "xyes" &&
+     test "x$with_libexpat_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "libexpat is requested but not found in the system.
+See \`config.log' for more details." "$LINENO" 5; }
+  fi
 fi
 
 if test "x$with_sqlite3" = "xyes"; then
@@ -6257,6 +6269,13 @@ LIBS=$LIBS_save
 CPPFLAGS=$CPPFLAGS_save
 
 
+  if test "x$have_sqlite3" != "xyes" &&
+     test "x$with_sqlite3_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "sqlite3 is requested but not found in the system.
+See \`config.log' for more details." "$LINENO" 5; }
+  fi
 fi
 
 if test "x$with_gnutls" = "xyes"; then
@@ -6559,6 +6578,11 @@ rm -f core conftest.err conftest.$ac_objext \
 
 $as_echo "#define HAVE_LIBGNUTLS 1" >>confdefs.h
 
+  elif test "x$with_gnutls_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "gnutls is requested but not found in the system.
+See \`config.log' for more details." "$LINENO" 5; }
   fi
 
 
@@ -6875,6 +6899,13 @@ fi
 LIBS=$LIBS_save
 CPPFLAGS=$CPPFLAGS_save
 
+  if test "x$have_openssl" != "xyes" &&
+     test "x$with_openssl_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "openssl is requested but not found in the system.
+See \`config.log' for more details." "$LINENO" 5; }
+  fi
 fi
 
 if test "x$with_libcares" = "xyes"; then
@@ -7038,6 +7069,13 @@ LIBS=$LIBS_save
 CPPFLAGS=$CPPFLAGS_save
 
 
+  if test "x$have_libcares" != "xyes" &&
+     test "x$with_libcares_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "libcares is requested but not found in the system.
+See \`config.log' for more details." "$LINENO" 5; }
+  fi
 fi
 
 # Check availability of libz
@@ -7119,6 +7157,12 @@ LIBS=$LIBS_save
 CPPFLAGS=$CPPFLAGS_save
 
 
+  if test "x$have_libz" != "xyes" && test "x$with_libz_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "libz is requested but not found in the system.
+See \`config.log' for more details." "$LINENO" 5; }
+  fi
 fi
 
 # Define variables based on the result of the checks for libraries.
@@ -7201,6 +7245,15 @@ else
 fi
 
 else
+  if test "x$enable_bittorrent_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "bittorrent is requested but cannot be enabled with current\
+ configuration.\
+ Make sure that dependent libraries are installed and configure script options\
+ are correct.
+See \`config.log' for more details." "$LINENO" 5; }
+  fi
   enable_bittorrent=no
    if false; then
   ENABLE_BITTORRENT_TRUE=
@@ -7226,6 +7279,15 @@ else
 fi
 
 else
+  if test "x$enable_metalink_requested" = "xyes"; then
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "metalink is requested but cannot be enabled with current\
+ configuration.\
+ Make sure that dependent libraries are installed and configure script options\
+ are correct.
+See \`config.log' for more details." "$LINENO" 5; }
+  fi
   enable_metalink=no
    if false; then
   ENABLE_METALINK_TRUE=
diff --git a/configure.ac b/configure.ac
index d7808695..4ece7e22 100644
--- a/configure.ac
+++ b/configure.ac
@@ -56,15 +56,25 @@ if test "x$with_libxml2" = "xyes"; then
   AM_PATH_XML2([2.6.24], [have_libxml2=yes])
   if test "x$have_libxml2" = "xyes"; then
     AC_DEFINE([HAVE_LIBXML2], [1], [Define to 1 if you have libxml2.])
+  elif test "x$with_libxml2_requested" = "xyes"; then
+    ARIA2_DEP_NOT_MET([libxml2])
   fi
 fi
 
 if test "x$with_libexpat" = "xyes" && test "x$have_libxml2" != "xyes"; then
   AM_PATH_LIBEXPAT
+  if test "x$have_libexpat" != "xyes" &&
+     test "x$with_libexpat_requested" = "xyes"; then
+    ARIA2_DEP_NOT_MET([libexpat])
+  fi
 fi
 
 if test "x$with_sqlite3" = "xyes"; then
   AM_PATH_SQLITE3
+  if test "x$have_sqlite3" != "xyes" &&
+     test "x$with_sqlite3_requested" = "xyes"; then
+    ARIA2_DEP_NOT_MET([sqlite3])
+  fi
 fi
 
 if test "x$with_gnutls" = "xyes"; then
@@ -79,6 +89,8 @@ if test "x$with_gnutls" = "xyes"; then
   fi
   if test "x$have_libgnutls" = "xyes"; then
     AC_DEFINE([HAVE_LIBGNUTLS], [1], [Define to 1 if you have libgnutls.])
+  elif test "x$with_gnutls_requested" = "xyes"; then
+    ARIA2_DEP_NOT_MET([gnutls])
   fi
   AC_SUBST(LIBGNUTLS_LIBS)
   AC_SUBST(LIBGNUTLS_CFLAGS)
@@ -93,15 +105,26 @@ fi
 
 if test "x$with_openssl" = "xyes" && test "x$have_libgnutls" != "xyes"; then
   AM_PATH_OPENSSL
+  if test "x$have_openssl" != "xyes" &&
+     test "x$with_openssl_requested" = "xyes"; then
+    ARIA2_DEP_NOT_MET([openssl])
+  fi
 fi
 
 if test "x$with_libcares" = "xyes"; then
   AM_PATH_LIBCARES
+  if test "x$have_libcares" != "xyes" &&
+     test "x$with_libcares_requested" = "xyes"; then
+    ARIA2_DEP_NOT_MET([libcares])
+  fi
 fi
 
 # Check availability of libz
 if test "x$with_libz" = "xyes"; then
   AM_PATH_LIBZ
+  if test "x$have_libz" != "xyes" && test "x$with_libz_requested" = "xyes"; then
+    ARIA2_DEP_NOT_MET([libz])
+  fi
 fi
 
 # Define variables based on the result of the checks for libraries.
@@ -131,6 +154,9 @@ if test "x$enable_bittorrent" = "xyes" &&
             [Define to 1 if BitTorrent support is enabled.])
   AM_CONDITIONAL([ENABLE_BITTORRENT], true)
 else
+  if test "x$enable_bittorrent_requested" = "xyes"; then
+    ARIA2_FET_NOT_SUPPORTED([bittorrent])
+  fi
   enable_bittorrent=no
   AM_CONDITIONAL([ENABLE_BITTORRENT], false)
 fi
@@ -141,6 +167,9 @@ if (test "x$have_libxml2" = "xyes" || test "x$have_libexpat" = "xyes") &&
             [Define to 1 if Metalink support is enabled.])
   AM_CONDITIONAL([ENABLE_METALINK], true)
 else
+  if test "x$enable_metalink_requested" = "xyes"; then
+    ARIA2_FET_NOT_SUPPORTED([metalink])
+  fi
   enable_metalink=no
   AM_CONDITIONAL([ENABLE_METALINK], false)
 fi
diff --git a/m4/aria2_arg.m4 b/m4/aria2_arg.m4
index 3d9b36da..eac010eb 100644
--- a/m4/aria2_arg.m4
+++ b/m4/aria2_arg.m4
@@ -1,15 +1,30 @@
 dnl ARIA2_ARG_WITH(PACKAGE)
 dnl wrapper for AC_ARG_WITH with default value 'yes'.
+dnl If --with-$1 is given explicitly, set with_$1_requested to given value.
 AC_DEFUN([ARIA2_ARG_WITH],
 [AC_ARG_WITH([$1],
 	AS_HELP_STRING([--with-$1], [Use $1 if it is installed.]),
-	[with_$1=$withval], [with_$1=yes])]
+	[with_$1_requested=$withval with_$1=$withval], [with_$1=yes])]
 )
 
 dnl ARIA2_ARG_ENABLE(FEATURE)
 dnl wrapper for AC_ARG_ENABLE with default value 'yes'.
+dnl If --enable-$1 is given explicitly, set enable_$1_requested to given value.
 AC_DEFUN([ARIA2_ARG_ENABLE],
 [AC_ARG_ENABLE([$1],
 	AS_HELP_STRING([--enable-$1], [Enable $1 support.]),
-	[enable_$1=$enableval], [enable_$1=yes])]
+	[enable_$1_requested=$enableval enable_$1=$enableval], [enable_$1=yes])]
 )
+
+dnl ARIA2_DEP_NOT_MET(PACKAGE)
+dnl Show error message PACKAGE is missing and exit.
+AC_DEFUN([ARIA2_DEP_NOT_MET],
+[AC_MSG_FAILURE([$1 is requested but not found in the system.])])
+
+dnl ARIA2_FET_NOT_SUPPORTED(FEATURE)
+dnl Show error message FEATURE can not be enabled and exit.
+AC_DEFUN([ARIA2_FET_NOT_SUPPORTED],
+[AC_MSG_FAILURE([$1 is requested but cannot be enabled with current\
+ configuration.\
+ Make sure that dependent libraries are installed and configure script options\
+ are correct.])])