diff --git a/src/hostspec.c b/src/hostspec.c
index 6a94400..ec1961e 100644
--- a/src/hostspec.c
+++ b/src/hostspec.c
@@ -15,6 +15,15 @@ static int dotted_mask(char *bitmask_string, unsigned char array[])
 	return 0;
 }
 
+static int dotted_mask(char *bitmask_string, unsigned char array[])
+{
+	unsigned char v4bits[4];
+	if (1 != inet_pton (AF_INET, bitmask_string, v4bits)) return -1;
+	memset (array, 0xff, IPV6_LEN-4);
+	memcpy (array + IPV6_LEN-4, v4bits, 4);
+	return 0;
+}
+
 /*
  * Fills in the netmask array given a numeric value.
  *