diff --git a/.changeset/rude-laws-join.md b/.changeset/rude-laws-join.md
new file mode 100644
index 00000000000..894032e2262
--- /dev/null
+++ b/.changeset/rude-laws-join.md
@@ -0,0 +1,5 @@
+---
+"@atproto/xrpc": patch
+---
+
+Explicitly allow "undefined" values in `headers`
diff --git a/packages/bsky/src/api/app/bsky/actor/getSuggestions.ts b/packages/bsky/src/api/app/bsky/actor/getSuggestions.ts
index 911b9cdcefe..4af0927feed 100644
--- a/packages/bsky/src/api/app/bsky/actor/getSuggestions.ts
+++ b/packages/bsky/src/api/app/bsky/actor/getSuggestions.ts
@@ -1,4 +1,6 @@
 import { mapDefined, noUndefinedVals } from '@atproto/common'
+import { AtpAgent } from '@atproto/api'
+import { HeadersMap } from '@atproto/xrpc'
 import AppContext from '../../../../context'
 import { Server } from '../../../../lexicon'
 import { QueryParams } from '../../../../lexicon/types/app/bsky/actor/getSuggestions'
@@ -12,7 +14,6 @@ import { Views } from '../../../../views'
 import { DataPlaneClient } from '../../../../data-plane'
 import { parseString } from '../../../../hydration/util'
 import { resHeaders } from '../../../util'
-import { AtpAgent } from '@atproto/api'
 
 export default function (server: Server, ctx: AppContext) {
   const getSuggestions = createPipeline(
@@ -144,12 +145,12 @@ type Context = {
 
 type Params = QueryParams & {
   hydrateCtx: HydrateCtx
-  headers: Record<string, string>
+  headers: HeadersMap
 }
 
 type Skeleton = {
   dids: string[]
   cursor?: string
   recId?: number
-  resHeaders?: Record<string, string>
+  resHeaders?: HeadersMap
 }
diff --git a/packages/bsky/src/api/app/bsky/graph/getSuggestedFollowsByActor.ts b/packages/bsky/src/api/app/bsky/graph/getSuggestedFollowsByActor.ts
index b8d2b563ba6..c7eec21bad9 100644
--- a/packages/bsky/src/api/app/bsky/graph/getSuggestedFollowsByActor.ts
+++ b/packages/bsky/src/api/app/bsky/graph/getSuggestedFollowsByActor.ts
@@ -1,6 +1,7 @@
 import { mapDefined, noUndefinedVals } from '@atproto/common'
 import { InvalidRequestError } from '@atproto/xrpc-server'
 import AtpAgent from '@atproto/api'
+import { HeadersMap } from '@atproto/xrpc'
 import { Server } from '../../../../lexicon'
 import { QueryParams } from '../../../../lexicon/types/app/bsky/graph/getSuggestedFollowsByActor'
 import AppContext from '../../../../context'
@@ -133,12 +134,12 @@ type Context = {
 
 type Params = QueryParams & {
   hydrateCtx: HydrateCtx & { viewer: string }
-  headers: Record<string, string>
+  headers: HeadersMap
 }
 
 type SkeletonState = {
   isFallback: boolean
   suggestedDids: string[]
   recId?: number
-  headers?: Record<string, string>
+  headers?: HeadersMap
 }
diff --git a/packages/bsky/tests/label-hydration.test.ts b/packages/bsky/tests/label-hydration.test.ts
index 9198c9fe29e..ad5ceb482f6 100644
--- a/packages/bsky/tests/label-hydration.test.ts
+++ b/packages/bsky/tests/label-hydration.test.ts
@@ -73,8 +73,11 @@ describe('label hydration', () => {
     expect(res.data.labels?.find((l) => l.src === labelerDid)?.val).toEqual(
       'misleading',
     )
-    const labelerHeaderDids = res.headers['atproto-content-labelers'].split(',')
-    expect(labelerHeaderDids.sort()).toEqual(
+    const labelerHeaderDids = res.headers['atproto-content-labelers']
+      ?.split(',')
+      .sort()
+
+    expect(labelerHeaderDids).toEqual(
       [alice, `${bob};redact`, labelerDid].sort(),
     )
   })
diff --git a/packages/pds/tests/proxied/read-after-write.test.ts b/packages/pds/tests/proxied/read-after-write.test.ts
index 0461efeac75..72aa7f59035 100644
--- a/packages/pds/tests/proxied/read-after-write.test.ts
+++ b/packages/pds/tests/proxied/read-after-write.test.ts
@@ -282,7 +282,7 @@ describe('proxy read after write', () => {
       { headers: { ...sc.getHeaders(alice) } },
     )
     const lag = res.headers['atproto-upstream-lag']
-    expect(lag).toBeDefined()
+    assert(lag !== undefined)
     const parsed = parseInt(lag)
     expect(parsed > 0).toBe(true)
   })
diff --git a/packages/xrpc/src/types.ts b/packages/xrpc/src/types.ts
index 11e88445271..bf79f25b2e6 100644
--- a/packages/xrpc/src/types.ts
+++ b/packages/xrpc/src/types.ts
@@ -2,7 +2,7 @@ import { z } from 'zod'
 import { ValidationError } from '@atproto/lexicon'
 
 export type QueryParams = Record<string, any>
-export type HeadersMap = Record<string, string>
+export type HeadersMap = Record<string, string | undefined>
 
 export type {
   /** @deprecated not to be confused with the WHATWG Headers constructor */