diff --git a/lib/ipv4.h b/lib/ipv4.h
index 5cb2835e..033116bb 100644
--- a/lib/ipv4.h
+++ b/lib/ipv4.h
@@ -53,7 +53,7 @@ typedef u32 ip_addr;
 #define ipa_ntoh(x) x = _MI(ntohl(_I(x)))
 #define ipa_classify(x) ipv4_classify(_I(x))
 #define ipa_opposite(x) _MI(_I(x) ^ 1)
-#define ipa_class_mask(x) x = _MI(ipv4_class_mask(_I(x)))
+#define ipa_class_mask(x) _MI(ipv4_class_mask(_I(x)))
 #define ipa_from_u32(x) _MI(x)
 #define ipa_to_u32(x) _I(x)
 #define ipa_compare(x,y) ipv4_compare(_I(x),_I(y))
diff --git a/proto/rip/rip.c b/proto/rip/rip.c
index 78eaa657..db84e87e 100644
--- a/proto/rip/rip.c
+++ b/proto/rip/rip.c
@@ -318,10 +318,8 @@ rip_process_packet( struct proto *p, struct rip_packet *packet, int num, ip_addr
 #ifndef IPV6
 	    ipa_ntoh( block->netmask );
 	    ipa_ntoh( block->nexthop );
-	    if (packet->heading.version == RIP_V1) {
-	      block->netmask = block->network; /* MJ: why are macros like this?! */
-	      ipa_class_mask( block->netmask );
-	    }
+	    if (packet->heading.version == RIP_V1)
+	      block->netmask = ipa_class_mask(block->network);
 #endif
 	    process_block( p, block, whotoldme );
 	  }