diff --git a/CHANGES b/CHANGES
index 555c56253..aa43d9ebd 100644
--- a/CHANGES
+++ b/CHANGES
@@ -13,6 +13,8 @@ Yang Tse (2 Jul 2008)
   will fallback to gettimeofday when the monotonic clock is unavailable at
   run-time.
 
+- The configure process will now halt when sed or grep are unavailable.
+
 Daniel Stenberg (1 Jul 2008)
 - Rolland Dudemaine provided fixes to get libcurl to build for the INTEGRITY
   operating system.
diff --git a/ares/configure.ac b/ares/configure.ac
index 12b61514f..797940af2 100644
--- a/ares/configure.ac
+++ b/ares/configure.ac
@@ -5,6 +5,22 @@ AM_CONFIG_HEADER([config.h])
 AM_MAINTAINER_MODE
 AM_INIT_AUTOMAKE
 
+dnl sed is mandatory for configure process
+AC_PATH_PROG([SED], [sed], [not found],
+  [$PATH:/usr/bin:/usr/local/bin])
+AC_SUBST([SED])
+if test -z "$SED" || test "$SED" = "not found"; then
+  AC_MSG_ERROR([Cannot continue without sed.])
+fi
+
+dnl grep is mandatory for configure process
+AC_PATH_PROG([GREP], [grep], [not found],
+  [$PATH:/usr/bin:/usr/local/bin])
+AC_SUBST([GREP])
+if test -z "$GREP" || test "$GREP" = "not found"; then
+  AC_MSG_ERROR([Cannot continue without grep.])
+fi
+
 dnl
 dnl Detect the canonical host and target build environment
 dnl
diff --git a/configure.ac b/configure.ac
index 09fccedfe..aef3577b3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,13 +36,20 @@ AC_CONFIG_SRCDIR([lib/urldata.h])
 AM_CONFIG_HEADER(lib/config.h src/config.h)
 AM_MAINTAINER_MODE
 
-dnl SED is needed by some of the tools
-AC_PATH_PROG( SED, sed, sed-was-not-found-by-configure,
-              $PATH:/usr/bin:/usr/local/bin)
-AC_SUBST(SED)
+dnl sed is mandatory for configure process
+AC_PATH_PROG([SED], [sed], [not found],
+  [$PATH:/usr/bin:/usr/local/bin])
+AC_SUBST([SED])
+if test -z "$SED" || test "$SED" = "not found"; then
+  AC_MSG_ERROR([Cannot continue without sed.])
+fi
 
-if test "x$SED" = "xsed-was-not-found-by-configure"; then
-  AC_MSG_WARN([sed was not found, this may ruin your chances to build fine])
+dnl grep is mandatory for configure process
+AC_PATH_PROG([GREP], [grep], [not found],
+  [$PATH:/usr/bin:/usr/local/bin])
+AC_SUBST([GREP])
+if test -z "$GREP" || test "$GREP" = "not found"; then
+  AC_MSG_ERROR([Cannot continue without grep.])
 fi
 
 dnl AR is used by libtool, and try the odd Solaris path too