diff --git a/lib/ipaddr.js.d.ts b/lib/ipaddr.js.d.ts
index 62afab3..048c6e4 100644
--- a/lib/ipaddr.js.d.ts
+++ b/lib/ipaddr.js.d.ts
@@ -22,7 +22,7 @@ declare module "ipaddr.js" {
         export function parse(addr: string): IPv4 | IPv6;
         export function parseCIDR(mask: string): [IPv4 | IPv6, number];
         export function process(addr: string): IPv4 | IPv6;
-        export function subnetMatch(addr: IPv4 | IPv6, rangeList: RangeList<IPv4 | IPv6>, defaultName?: string): string;
+        export function subnetMatch<L extends RangeList<IPv4 | IPv6>, D extends string = "unicast">(addr: IPv4 | IPv6, rangeList: L, defaultName?: D): keyof L | D;
 
         export class IPv4 extends IP {
             static broadcastAddressFromCIDR(addr: string): IPv4;
@@ -40,7 +40,7 @@ declare module "ipaddr.js" {
             kind(): 'ipv4';
             match(what: IPv4 | IPv6 | [IPv4 | IPv6, number], bits?: number): boolean;
             range(): IPv4Range;
-            subnetMatch(rangeList: RangeList<IPv4>, defaultName?: string): string;
+            subnetMatch<L extends RangeList<IPv4>, D extends string = "unicast">(rangeList: L, defaultName?: D): keyof L | D;
             toIPv4MappedAddress(): IPv6;
         }
 
@@ -61,7 +61,7 @@ declare module "ipaddr.js" {
             kind(): 'ipv6';
             match(what: IPv4 | IPv6 | [IPv4 | IPv6, number], bits?: number): boolean;
             range(): IPv6Range;
-            subnetMatch(rangeList: RangeList<IPv6>, defaultName?: string): string;
+            subnetMatch<L extends RangeList<IPv6>, D extends string = "unicast">(rangeList: L, defaultName?: D): keyof L | D;
             toIPv4Address(): IPv4;
             toRFC5952String(): string;
         }