diff --git a/src/configure.in b/src/configure.in
index 28fd8c1..37c5ff8 100644
--- a/src/configure.in
+++ b/src/configure.in
@@ -14,6 +14,7 @@
 AC_PROG_CC	dnl required by almost everything
 AC_PROG_CPP	dnl required by header file checks
 AC_PROGRAM_EGREP dnl required by AC_EGREP_CPP
+AC_PROG_FGREP	dnl finds working grep -F
 AC_ISC_POSIX	dnl required by AC_C_CROSS
 AC_PROG_AWK	dnl required for "make html" in ../doc
 
@@ -936,7 +937,7 @@
 	  PERL_CFLAGS=`echo "$perlcppflags" | sed -e 's/-pipe //' -e 's/-W[[^ ]]*//'`
 	fi
 	if test "X$perlldflags" != "X"; then
-	  if test "X`echo \"$LDFLAGS\" | grep -F -e \"$perlldflags\"`" = "X"; then
+	  if test "X`echo \"$LDFLAGS\" | $FGREP -e \"$perlldflags\"`" = "X"; then
 	    LDFLAGS="$perlldflags $LDFLAGS"
 	  fi
 	fi
@@ -1727,7 +1728,7 @@
 	  dnl configure, so strip these flags first (if present)
 	  rubyldflags=`echo "$rubyldflags" | sed -e 's/-arch\ ppc//' -e 's/-arch\ i386//' -e 's/-arch\ x86_64//'`
 	  if test "X$rubyldflags" != "X"; then
-	    if test "X`echo \"$LDFLAGS\" | grep -F -e \"$rubyldflags\"`" = "X"; then
+	    if test "X`echo \"$LDFLAGS\" | $FGREP -e \"$rubyldflags\"`" = "X"; then
 	      LDFLAGS="$rubyldflags $LDFLAGS"
 	    fi
 	  fi