diff -Naur grep-2.5.4.183-9159.orig/configure grep-2.5.4.183-9159/configure
--- grep-2.5.4.183-9159.orig/configure	2010-03-17 17:01:06.000000000 +0000
+++ grep-2.5.4.183-9159/configure	2010-03-19 22:13:34.000000000 +0000
@@ -14652,7 +14652,7 @@
               return 1;
 
             /* Ensure that [b-a] is diagnosed as invalid. */
-            re_set_syntax (RE_SYNTAX_POSIX_EGREP);
+            re_set_syntax (RE_SYNTAX_POSIX_EGREP | RE_NO_EMPTY_RANGES);
             memset (&regex, 0, sizeof regex);
             s = re_compile_pattern ("a[b-a]", 6, &regex);
             if (s == 0)
diff -Naur grep-2.5.4.183-9159.orig/src/search.c grep-2.5.4.183-9159/src/search.c
--- grep-2.5.4.183-9159.orig/src/search.c	2010-03-17 10:23:12.000000000 +0000
+++ grep-2.5.4.183-9159/src/search.c	2010-03-19 22:14:06.000000000 +0000
@@ -368,7 +368,7 @@
 
 COMPILE_FCT(Ecompile)
 {
-  return GEAcompile (pattern, size, RE_SYNTAX_POSIX_EGREP);
+  return GEAcompile (pattern, size, RE_SYNTAX_POSIX_EGREP | RE_NO_EMPTY_RANGES);
 }
 #endif /* !EGREP_PROGRAM */