diff --git a/inet.go b/inet.go
index 25e56170..a343f5e2 100644
--- a/inet.go
+++ b/inet.go
@@ -4,6 +4,7 @@ import (
 	"database/sql/driver"
 	"fmt"
 	"net"
+	"strings"
 )
 
 // Network address family is dependent on server socket.h value for AF_INET.
@@ -52,17 +53,17 @@ func (dst *Inet) Set(src interface{}) error {
 				return fmt.Errorf("unable to parse inet address: %s", value)
 			}
 
-			if ipv4 := ip.To4(); ipv4 != nil {
+			if ipv4 := maybeGetIPv4(value, ip); ipv4 != nil {
 				ipnet = &net.IPNet{IP: ipv4, Mask: net.CIDRMask(32, 32)}
 			} else {
 				ipnet = &net.IPNet{IP: ip, Mask: net.CIDRMask(128, 128)}
 			}
 		} else {
 			ipnet.IP = ip
-			if ipv4 := ipnet.IP.To4(); ipv4 != nil {
+			if ipv4 := maybeGetIPv4(value, ipnet.IP); ipv4 != nil {
 				ipnet.IP = ipv4
 				if len(ipnet.Mask) == 16 {
-					ipnet.Mask = ipnet.Mask[12:] // Needed if input is IPv4-mapped IPv6.
+					ipnet.Mask = ipnet.Mask[12:] // Not sure this is ever needed.
 				}
 			}
 		}
@@ -96,6 +97,25 @@ func (dst *Inet) Set(src interface{}) error {
 	return nil
 }
 
+// Convert the net.IP to IPv4, if appropriate.
+//
+// When parsing a string to a net.IP using net.ParseIP() and the like, we get a
+// 16 byte slice for IPv4 addresses as well as IPv6 addresses. This function
+// calls To4() to convert them to a 4 byte slice. This is useful as it allows
+// users of the net.IP check for IPv4 addresses based on the length and makes
+// it clear we are handling IPv4 as opposed to IPv6 or IPv4-mapped IPv6
+// addresses.
+func maybeGetIPv4(input string, ip net.IP) net.IP {
+	// Do not do this if the provided input looks like IPv6. This is because
+	// To4() on IPv4-mapped IPv6 addresses converts them to IPv4, which behave
+	// different in some cases.
+	if strings.Contains(input, ":") {
+		return nil
+	}
+
+	return ip.To4()
+}
+
 func (dst Inet) Get() interface{} {
 	switch dst.Status {
 	case Present:
diff --git a/inet_test.go b/inet_test.go
index badbf82e..52759371 100644
--- a/inet_test.go
+++ b/inet_test.go
@@ -57,7 +57,7 @@ func TestInetSet(t *testing.T) {
 		{source: "2607:f8b0:4009:80b::200e", result: pgtype.Inet{IPNet: mustParseInet(t, "2607:f8b0:4009:80b::200e"), Status: pgtype.Present}},
 		{source: net.ParseIP(""), result: pgtype.Inet{Status: pgtype.Null}},
 		{source: "0.0.0.0/8", result: pgtype.Inet{IPNet: mustParseInet(t, "0.0.0.0/8"), Status: pgtype.Present}},
-		{source: "::ffff:0.0.0.0/104", result: pgtype.Inet{IPNet: &net.IPNet{IP: net.ParseIP("0.0.0.0").To4(), Mask: net.CIDRMask(8, 32)}, Status: pgtype.Present}},
+		{source: "::ffff:0.0.0.0/104", result: pgtype.Inet{IPNet: &net.IPNet{IP: net.ParseIP("::ffff:0.0.0.0"), Mask: net.CIDRMask(104, 128)}, Status: pgtype.Present}},
 	}
 
 	for i, tt := range successfulTests {