diff --git a/bird.conf b/bird.conf
index 0b866f62..46633bf2 100644
--- a/bird.conf
+++ b/bird.conf
@@ -38,9 +38,8 @@ ip p;
 	if 1234 = i then printn "."; else { print "*** FAIL: if 1 else"; }
 	if 1 <= 1 then printn "."; else { print "*** FAIL: test 3"; }
 	if 1234 < 1234 then { print "*** FAIL: test 4"; quitbird; } else print "ok";
-
-	print "  data types; must be true: " 1.2.3.4 = 1.2.3.4 "," 1 ~ [1,2,3] "," 5 ~ [1..20] "," 2 ~ [ 1, 2, 3 ] "," 5 ~ [ 4 .. 7 ] "," 1.2.3.4 ~ [ 1.2.3.3..1.2.3.5 ] "," 1.2.3.4 ~ 1.2.3.4/8 "," 1.2.3.4/8 ~ 1.2.3.4/8 "," 1.2.3.4/8 ~ 1.2.3.4/8+ "," 1.2.3.4/16 ~ 1.2.3.4/8{ 15 , 16 } "," defined(1) "," defined(1.2.3.4);
-	print "  data types: must be false: " 1 ~ [ 2, 3, 4 ] "," 5 ~ [ 2, 3, 4, 7..11 ] "," 1.2.3.4 ~ [ 1.2.3.3, 1.2.3.5 ] "," (1,2) > (2,2) "," (1,1) > (1,1) "," 1.2.3.4/8 ~ 1.2.3.4/8- "," 1.2.3.4/17 ~ 1.2.3.4/8{ 15 , 16 };
+	print "  data types; must be true: " 1.2.3.4 = 1.2.3.4 "," 1 ~ [1,2,3] "," 5 ~ [1..20] "," 2 ~ [ 1, 2, 3 ] "," 5 ~ [ 4 .. 7 ] "," 1.2.3.4 ~ [ 1.2.3.3..1.2.3.5 ] "," 1.2.3.4 ~ 1.2.3.4/8 "," 1.2.3.4/8 ~ 1.2.3.4/8 "," 1.2.3.4/8 ~ [ 1.2.3.4/8+ ] "," 1.2.3.4/16 ~ [ 1.2.3.4/8{ 15 , 16 } ] "," defined(1) "," defined(1.2.3.4);
+	print "  data types: must be false: " 1 ~ [ 2, 3, 4 ] "," 5 ~ [ 2, 3, 4, 7..11 ] "," 1.2.3.4 ~ [ 1.2.3.3, 1.2.3.5 ] "," (1,2) > (2,2) "," (1,1) > (1,1) "," 1.2.3.4/8 ~ [ 1.2.3.4/8- ] "," 1.2.3.4/17 ~ [ 1.2.3.4/8{ 15 , 16 } ];
 
 	px = 1.2.3.4/18;
 	print "Testing prefixes: 1.2.3.4/18 = " px;
diff --git a/filter/config.Y b/filter/config.Y
index b410397b..8f41f443 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -235,7 +235,7 @@ constant:
  | TEXT   { $$ = f_new_inst(); $$->code = 'c'; $$->a1.i = T_STRING; $$->a2.p = $1; }
  | pair   { $$ = f_new_inst(); $$->code = 'c'; $$->a1.i = T_PAIR;  $$->a2.i = $1; }
  | ipa	   { NEW_F_VAL; $$ = f_new_inst(); $$->code = 'C'; $$->a1.p = val; *val = $1; }
- | prefix  {NEW_F_VAL; $$ = f_new_inst(); $$->code = 'C'; $$->a1.p = val; *val = $1; }
+ | prefix_s {NEW_F_VAL; $$ = f_new_inst(); $$->code = 'C'; $$->a1.p = val; *val = $1; }
  | '[' set_items ']' { printf( "We've got a set here..." ); $$ = f_new_inst(); $$->code = 'c'; $$->a1.i = T_SET; $$->a2.p = build_tree($2); printf( "ook\n" ); }
  ;
 
diff --git a/filter/filter.c b/filter/filter.c
index a6030ae7..0dc4b213 100644
--- a/filter/filter.c
+++ b/filter/filter.c
@@ -6,6 +6,8 @@
  *	Can be freely distributed and used under the terms of the GNU GPL.
  *
  * 	Notice that pair is stored as integer: first << 16 | second
+ *
+ *	FIXME: Check if prefixes are really prefixes.
  */
 
 #include <stdio.h>
@@ -111,7 +113,7 @@ val_in_range(struct f_val v1, struct f_val v2)
   if (res != CMP_ERROR)
     return res;
 
-  if (((v1.type == T_INT) || (v1.type == T_IP)) && (v2.type == T_SET)) {
+  if (((v1.type == T_INT) || ((v1.type == T_IP) || (v1.type == T_PREFIX)) && (v2.type == T_SET))) {
     struct f_tree *n;
     n = find_tree(v2.val.t, v1);
     if (!n)