diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4bd79b9d7a2..1bb5c6a2977 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20612,6 +20612,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
          * * Ternary.False if they are not related.
          */
         function isRelatedTo(originalSource: Type, originalTarget: Type, recursionFlags: RecursionFlags = RecursionFlags.Both, reportErrors = false, headMessage?: DiagnosticMessage, intersectionState = IntersectionState.None): Ternary {
+            if (originalSource === originalTarget) return Ternary.True;
+
             // Before normalization: if `source` is type an object type, and `target` is primitive,
             // skip all the checks we don't need and just return `isSimpleTypeRelatedTo` result
             if (originalSource.flags & TypeFlags.Object && originalTarget.flags & TypeFlags.Primitive) {
diff --git a/tests/baselines/reference/identityAndDivergentNormalizedTypes.symbols b/tests/baselines/reference/identityAndDivergentNormalizedTypes.symbols
new file mode 100644
index 00000000000..b65ab20b3a4
--- /dev/null
+++ b/tests/baselines/reference/identityAndDivergentNormalizedTypes.symbols
@@ -0,0 +1,96 @@
+=== tests/cases/compiler/identityAndDivergentNormalizedTypes.ts ===
+// Repros from #53998
+
+type ApiPost =
+>ApiPost : Symbol(ApiPost, Decl(identityAndDivergentNormalizedTypes.ts, 0, 0))
+
+    | {
+        path: "/login";
+>path : Symbol(path, Decl(identityAndDivergentNormalizedTypes.ts, 3, 7))
+
+        body: {};
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 4, 23))
+    }
+    | {
+        path: "/user";
+>path : Symbol(path, Decl(identityAndDivergentNormalizedTypes.ts, 7, 7))
+
+        body: { name: string; };
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 8, 22))
+>name : Symbol(name, Decl(identityAndDivergentNormalizedTypes.ts, 9, 15))
+    }
+
+type PostPath = ApiPost["path"];
+>PostPath : Symbol(PostPath, Decl(identityAndDivergentNormalizedTypes.ts, 10, 5))
+>ApiPost : Symbol(ApiPost, Decl(identityAndDivergentNormalizedTypes.ts, 0, 0))
+
+type PostBody<PATH extends PostPath> = Extract<ApiPost, { path: PATH }>["body"];
+>PostBody : Symbol(PostBody, Decl(identityAndDivergentNormalizedTypes.ts, 12, 32))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 14, 14))
+>PostPath : Symbol(PostPath, Decl(identityAndDivergentNormalizedTypes.ts, 10, 5))
+>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
+>ApiPost : Symbol(ApiPost, Decl(identityAndDivergentNormalizedTypes.ts, 0, 0))
+>path : Symbol(path, Decl(identityAndDivergentNormalizedTypes.ts, 14, 57))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 14, 14))
+
+const post = <PATH extends PostPath>(
+>post : Symbol(post, Decl(identityAndDivergentNormalizedTypes.ts, 16, 5))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 16, 14))
+>PostPath : Symbol(PostPath, Decl(identityAndDivergentNormalizedTypes.ts, 10, 5))
+
+    path: PATH,
+>path : Symbol(path, Decl(identityAndDivergentNormalizedTypes.ts, 16, 37))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 16, 14))
+
+    {body, ...options}: Omit<RequestInit, 'body'> & {body: PostBody<PATH>}
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 18, 5))
+>options : Symbol(options, Decl(identityAndDivergentNormalizedTypes.ts, 18, 10))
+>Omit : Symbol(Omit, Decl(lib.es5.d.ts, --, --))
+>RequestInit : Symbol(RequestInit, Decl(lib.dom.d.ts, --, --))
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 18, 53))
+>PostBody : Symbol(PostBody, Decl(identityAndDivergentNormalizedTypes.ts, 12, 32))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 16, 14))
+
+) => {
+}
+
+const tmp = <PATH extends PostPath>(
+>tmp : Symbol(tmp, Decl(identityAndDivergentNormalizedTypes.ts, 22, 5))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 22, 13))
+>PostPath : Symbol(PostPath, Decl(identityAndDivergentNormalizedTypes.ts, 10, 5))
+
+  path: PATH,
+>path : Symbol(path, Decl(identityAndDivergentNormalizedTypes.ts, 22, 36))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 22, 13))
+
+  body: PostBody<PATH>
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 23, 13))
+>PostBody : Symbol(PostBody, Decl(identityAndDivergentNormalizedTypes.ts, 12, 32))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 22, 13))
+
+) => {
+  post<PATH>(path, { body })
+>post : Symbol(post, Decl(identityAndDivergentNormalizedTypes.ts, 16, 5))
+>PATH : Symbol(PATH, Decl(identityAndDivergentNormalizedTypes.ts, 22, 13))
+>path : Symbol(path, Decl(identityAndDivergentNormalizedTypes.ts, 22, 36))
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 26, 20))
+}
+
+function fx1<P extends PostPath>(x: { body: PostBody<P> }, y: { body: PostBody<P> }) {
+>fx1 : Symbol(fx1, Decl(identityAndDivergentNormalizedTypes.ts, 27, 1))
+>P : Symbol(P, Decl(identityAndDivergentNormalizedTypes.ts, 29, 13))
+>PostPath : Symbol(PostPath, Decl(identityAndDivergentNormalizedTypes.ts, 10, 5))
+>x : Symbol(x, Decl(identityAndDivergentNormalizedTypes.ts, 29, 33))
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 29, 37))
+>PostBody : Symbol(PostBody, Decl(identityAndDivergentNormalizedTypes.ts, 12, 32))
+>P : Symbol(P, Decl(identityAndDivergentNormalizedTypes.ts, 29, 13))
+>y : Symbol(y, Decl(identityAndDivergentNormalizedTypes.ts, 29, 58))
+>body : Symbol(body, Decl(identityAndDivergentNormalizedTypes.ts, 29, 63))
+>PostBody : Symbol(PostBody, Decl(identityAndDivergentNormalizedTypes.ts, 12, 32))
+>P : Symbol(P, Decl(identityAndDivergentNormalizedTypes.ts, 29, 13))
+
+    x = y;
+>x : Symbol(x, Decl(identityAndDivergentNormalizedTypes.ts, 29, 33))
+>y : Symbol(y, Decl(identityAndDivergentNormalizedTypes.ts, 29, 58))
+}
+
diff --git a/tests/baselines/reference/identityAndDivergentNormalizedTypes.types b/tests/baselines/reference/identityAndDivergentNormalizedTypes.types
new file mode 100644
index 00000000000..15dff40bd92
--- /dev/null
+++ b/tests/baselines/reference/identityAndDivergentNormalizedTypes.types
@@ -0,0 +1,76 @@
+=== tests/cases/compiler/identityAndDivergentNormalizedTypes.ts ===
+// Repros from #53998
+
+type ApiPost =
+>ApiPost : { path: "/login"; body: {}; } | { path: "/user"; body: {    name: string;}; }
+
+    | {
+        path: "/login";
+>path : "/login"
+
+        body: {};
+>body : {}
+    }
+    | {
+        path: "/user";
+>path : "/user"
+
+        body: { name: string; };
+>body : { name: string; }
+>name : string
+    }
+
+type PostPath = ApiPost["path"];
+>PostPath : "/login" | "/user"
+
+type PostBody<PATH extends PostPath> = Extract<ApiPost, { path: PATH }>["body"];
+>PostBody : PostBody<PATH>
+>path : PATH
+
+const post = <PATH extends PostPath>(
+>post : <PATH extends "/login" | "/user">(path: PATH, { body, ...options }: Omit<RequestInit, "body"> & { body: PostBody<PATH>; }) => void
+><PATH extends PostPath>(    path: PATH,    {body, ...options}: Omit<RequestInit, 'body'> & {body: PostBody<PATH>}) => {} : <PATH extends "/login" | "/user">(path: PATH, { body, ...options }: Omit<RequestInit, "body"> & { body: PostBody<PATH>; }) => void
+
+    path: PATH,
+>path : PATH
+
+    {body, ...options}: Omit<RequestInit, 'body'> & {body: PostBody<PATH>}
+>body : PostBody<PATH>
+>options : { cache?: RequestCache | undefined; credentials?: RequestCredentials | undefined; headers?: HeadersInit | undefined; integrity?: string | undefined; keepalive?: boolean | undefined; method?: string | undefined; mode?: RequestMode | undefined; redirect?: RequestRedirect | undefined; referrer?: string | undefined; referrerPolicy?: ReferrerPolicy | undefined; signal?: AbortSignal | null | undefined; window?: null | undefined; }
+>body : PostBody<PATH>
+
+) => {
+}
+
+const tmp = <PATH extends PostPath>(
+>tmp : <PATH extends "/login" | "/user">(path: PATH, body: PostBody<PATH>) => void
+><PATH extends PostPath>(  path: PATH,  body: PostBody<PATH>) => {  post<PATH>(path, { body })} : <PATH extends "/login" | "/user">(path: PATH, body: PostBody<PATH>) => void
+
+  path: PATH,
+>path : PATH
+
+  body: PostBody<PATH>
+>body : PostBody<PATH>
+
+) => {
+  post<PATH>(path, { body })
+>post<PATH>(path, { body }) : void
+>post : <PATH extends "/login" | "/user">(path: PATH, { body, ...options }: Omit<RequestInit, "body"> & { body: PostBody<PATH>; }) => void
+>path : PATH
+>{ body } : { body: PostBody<PATH>; }
+>body : PostBody<PATH>
+}
+
+function fx1<P extends PostPath>(x: { body: PostBody<P> }, y: { body: PostBody<P> }) {
+>fx1 : <P extends "/login" | "/user">(x: {    body: PostBody<P>;}, y: {    body: PostBody<P>;}) => void
+>x : { body: PostBody<P>; }
+>body : PostBody<P>
+>y : { body: PostBody<P>; }
+>body : PostBody<P>
+
+    x = y;
+>x = y : { body: PostBody<P>; }
+>x : { body: PostBody<P>; }
+>y : { body: PostBody<P>; }
+}
+
diff --git a/tests/cases/compiler/identityAndDivergentNormalizedTypes.ts b/tests/cases/compiler/identityAndDivergentNormalizedTypes.ts
new file mode 100644
index 00000000000..dc0059ef263
--- /dev/null
+++ b/tests/cases/compiler/identityAndDivergentNormalizedTypes.ts
@@ -0,0 +1,35 @@
+// @strict: true
+// @noEmit: true
+
+// Repros from #53998
+
+type ApiPost =
+    | {
+        path: "/login";
+        body: {};
+    }
+    | {
+        path: "/user";
+        body: { name: string; };
+    }
+
+type PostPath = ApiPost["path"];
+
+type PostBody<PATH extends PostPath> = Extract<ApiPost, { path: PATH }>["body"];
+
+const post = <PATH extends PostPath>(
+    path: PATH,
+    {body, ...options}: Omit<RequestInit, 'body'> & {body: PostBody<PATH>}
+) => {
+}
+
+const tmp = <PATH extends PostPath>(
+  path: PATH,
+  body: PostBody<PATH>
+) => {
+  post<PATH>(path, { body })
+}
+
+function fx1<P extends PostPath>(x: { body: PostBody<P> }, y: { body: PostBody<P> }) {
+    x = y;
+}