diff --git a/types/sdp-transform/index.d.ts b/types/sdp-transform/index.d.ts
index 906cb27c984f3a..65f6cd552b34ce 100644
--- a/types/sdp-transform/index.d.ts
+++ b/types/sdp-transform/index.d.ts
@@ -110,7 +110,7 @@ export interface MediaAttributes extends SharedAttributes {
     // a=mid:foo
     mid?: string;
     // a=msid:0c8b064d-d807-43b4-b434-f92a889d8587 98178685-d409-46e0-8e16-7ef0db0db64a
-    msid?: string;
+    msid?: { id: string; appdata?: string }[];
     // a=ptime:20
     ptime?: number;
     // a=maxptime:60
@@ -304,7 +304,7 @@ export interface SharedAttributes {
 }
 
 export interface ParamMap {
-    [paramName: string]: number | string;
+    [paramName: string]: number | string | undefined;
 }
 
 export function write(description: SessionDescription): string;
diff --git a/types/sdp-transform/package.json b/types/sdp-transform/package.json
index 5f24ede1474201..8782ce003df33c 100644
--- a/types/sdp-transform/package.json
+++ b/types/sdp-transform/package.json
@@ -1,7 +1,7 @@
 {
     "private": true,
     "name": "@types/sdp-transform",
-    "version": "2.15.9999",
+    "version": "3.0.9999",
     "projects": [
         "https://github.com/clux/sdp-transform#readme"
     ],
diff --git a/types/sdp-transform/sdp-transform-tests.ts b/types/sdp-transform/sdp-transform-tests.ts
index 8d5c3aea2cfc96..ea1ecceb528026 100644
--- a/types/sdp-transform/sdp-transform-tests.ts
+++ b/types/sdp-transform/sdp-transform-tests.ts
@@ -121,3 +121,19 @@ function test_datachannel_media_description() {
     const port = parsed.media[0].port;
     port; // $ExpectType number
 }
+
+function test_msid_attribute() {
+    const session: SessionDescription = parse("");
+    session.media[0].msid = [
+        { id: "0c8b064d-d807-43b4-b434-f92a889d8587" },
+        { id: "98178685-d409-46e0-8e16-7ef0db0db64a", appdata: "my-track-id" },
+    ];
+
+    const sdp: string = write(session);
+    const parsed = parse(sdp);
+    const msid = parsed.media[0].msid!;
+    msid[0].id; // $ExpectType string
+    msid[0].appdata; // $ExpectType string | undefined
+    msid[1].id; // $ExpectType string
+    msid[1].appdata; // $ExpectType string | undefined
+}