diff --git a/sys/netpfil/ipfilter/netinet/radix_ipf.c b/sys/netpfil/ipfilter/netinet/radix_ipf.c
index 031452da9f4..0ab4431c21c 100644
--- a/sys/netpfil/ipfilter/netinet/radix_ipf.c
+++ b/sys/netpfil/ipfilter/netinet/radix_ipf.c
@@ -54,6 +54,8 @@ static ipf_rdx_node_t *ipf_rx_match(ipf_rdx_head_t *, addrfamily_t *);
 /* ------------------------------------------------------------------------ */
 /* Function:    count_mask_bits                                             */
 /* Returns:     number of consecutive bits starting at "mask".              */
+/* Parameters:  mask(I)  - netmask                                          */
+/*              lastp(I) - pointer to last word with a bit set              */
 /*                                                                          */
 /* Count the number of bits set in the address section of addrfamily_t and  */
 /* return both that number and a pointer to the last word with a bit set if */