diff --git a/conf/confbase.Y b/conf/confbase.Y
index c2d647eb..55615528 100644
--- a/conf/confbase.Y
+++ b/conf/confbase.Y
@@ -177,10 +177,6 @@ pxlen4:
      if ($2 > IP4_MAX_PREFIX_LENGTH) cf_error("Invalid prefix length %u", $2);
      $$ = $2;
    }
- | ':' IP4 {
-     $$ = ip4_masklen($2);
-     if ($$ == 255) cf_error("Invalid netmask %I4", $2);
-   }
  ;
 
 net_ip4_: IP4 pxlen4
diff --git a/doc/bird.sgml b/doc/bird.sgml
index 04f9258b..5ed816e8 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -1234,8 +1234,7 @@ foot).
 	operator <cf/.type/. The type may be:
 
 	<cf/NET_IP4/ and <cf/NET_IP6/ prefixes hold an IP prefix. The literals
-	are written as <cf><m/ipaddress//<m/pxlen/</cf>,
-	or <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
+	are written as <cf><m/ipaddress//<m/pxlen/</cf>. There are two special
 	operators on these: <cf/.ip/ which extracts the IP address from the
 	pair, and <cf/.len/, which separates prefix length from the pair.
 	So <cf>1.2.0.0/16.len = 16</cf> is true.
diff --git a/filter/test.conf2 b/filter/test.conf2
index 2a5d896b..83554952 100644
--- a/filter/test.conf2
+++ b/filter/test.conf2
@@ -76,8 +76,8 @@ protocol static {
 	route 62.168.0.0/25 reject;
 	route 1.2.3.4/32 via 195.113.31.124;
 	route 10.0.0.0/8 reject;
-	route 10.1.1.0:255.255.255.0 via 62.168.0.3;
-	route 10.1.2.0:255.255.255.0 via 62.168.0.3;
-	route 10.1.3.0:255.255.255.0 via 62.168.0.4;
+	route 10.1.1.0/24 via 62.168.0.3;
+	route 10.1.2.0/24 via 62.168.0.3;
+	route 10.1.3.0/24 via 62.168.0.4;
 	route 10.2.0.0/24 via "arc0";
 }