--- spamass-milter.cpp	2013-12-09 14:35:53.000000000 +0900
+++ spamass-milter.cpp	2013-12-09 14:37:43.000000000 +0900
@@ -2044,7 +2044,7 @@ 
 						exit(1);
 					}
 					mask.s_addr = htonl(~((1L << (32 - bits)) - 1) & 0xffffffff);
-				} else if (!inet_pton(AF_INET6, tmask, &mask))
+				} else if (!inet_pton(AF_INET, tmask, &mask))
 				{
 					fprintf(stderr, "Could not parse \"%s\" as a netmask\n", tmask);
 					exit(1);