diff --git a/flake.nix b/flake.nix
index 73b9488..f1627fd 100644
--- a/flake.nix
+++ b/flake.nix
@@ -42,7 +42,7 @@
             deno
             nixpkgs-fmt
             # can't use slim here as long as we still publish with npm.
-            # TODO(@joscha) change this once we only publish to jsr
+            # TODO(@joscha) change this once we only publish to jsr only
             nodejs_20
             # For openapi-generator
             # If more dependencies are needed, investigate whether to load https://github.com/OpenAPITools/openapi-generator/blob/master/flake.nix
diff --git a/package.json b/package.json
index bec163d..bfa5b3f 100644
--- a/package.json
+++ b/package.json
@@ -14,5 +14,8 @@
     "author": "Planet A Ventures <dev@planet-a.com>",
     "license": "MIT",
     "private": true,
-    "type": "module"
+    "type": "module",
+    "engines": {
+        "node": ">=20"
+    }
 }
diff --git a/scripts/build_npm.ts b/scripts/build_npm.ts
index 8a65863..25323a9 100644
--- a/scripts/build_npm.ts
+++ b/scripts/build_npm.ts
@@ -54,6 +54,9 @@ await build({
             access: 'public',
         },
         keywords: ['affinity', 'crm', 'node', 'api', 'sdk'],
+        engines: {
+            node: '>=20',
+        },
     },
     postBuild() {
         // steps to run after building and before running the tests
diff --git a/src/v1/entity_files.ts b/src/v1/entity_files.ts
index cb9275a..34b5c9a 100644
--- a/src/v1/entity_files.ts
+++ b/src/v1/entity_files.ts
@@ -1,5 +1,7 @@
 import { assert } from '@std/assert'
 import type { AxiosInstance } from 'axios'
+import fs from 'node:fs'
+import path from 'node:path'
 import type { Readable } from 'node:stream'
 import { defaultTransformers } from './axios_default_transformers.ts'
 import { createSearchIteratorFn } from './create_search_iterator_fn.ts'
@@ -63,9 +65,11 @@ export type PagedEntityFileResponse = Replace<PagedEntityFileResponseRaw, {
     entity_files: EntityFile[]
 }>
 
+export type SupportedFileType = File | string
+
 export type UploadEntityFileRequest =
     & {
-        files: File[]
+        files: SupportedFileType[]
     }
     & RequireOnlyOne<EntityRequestFilter, keyof EntityRequestFilter>
 
@@ -188,18 +192,9 @@ export class EntityFiles {
         const formData = new FormData()
         const { files } = params
         assert(files.length, 'At least one file must be provided')
-        if (files.length === 1) {
-            // Append the file as 'file' if only one file is provided
-            // it's a bit odd that the Affinity API expects the file to be sent in a different
-            // parameter, but maybe there is an implementation detail that treats multiple files
-            // differently to a single one, so we're complying with the API here
-            const [file] = files
-            formData.append('file', file, file.name)
-        } else {
-            files.forEach((file) => {
-                formData.append('files[]', file, file.name)
-            })
-        }
+
+        await Promise.all(files.map((file) => appendToFormData(formData, file)))
+
         if (params.person_id) {
             formData.append('person_id', params.person_id.toString())
         } else if (params.organization_id) {
@@ -227,3 +222,32 @@ export class EntityFiles {
         return response.data.success === true
     }
 }
+
+function isFile(file: unknown): file is File {
+    return file instanceof File
+}
+
+async function appendToFormData(formData: FormData, file: SupportedFileType) {
+    if (typeof file === 'string') {
+        formData.append('files[]', await openAsBlob(file), path.basename(file))
+    } else if (isFile(file)) {
+        formData.append('files[]', file)
+    } else {
+        throw new Error('Unsupported file type')
+    }
+}
+
+// TODO(@joscha): replace with `import { openAsBlob } from "node:fs";` ASAP
+function openAsBlob(filePath: string): Promise<Blob> {
+    return new Promise((resolve, reject) => {
+        const fileStream = fs.createReadStream(filePath)
+        const chunks: (string | ArrayBuffer)[] = []
+        fileStream.on('data', (chunk) => {
+            chunks.push(typeof chunk === 'string' ? chunk : chunk.buffer)
+        })
+        fileStream.on('end', () => {
+            resolve(new Blob(chunks))
+        })
+        fileStream.on('error', reject)
+    })
+}
diff --git a/src/v1/tests/__snapshots__/entity_files_test.ts.snap b/src/v1/tests/__snapshots__/entity_files_test.ts.snap
index c46efcf..46d718d 100644
--- a/src/v1/tests/__snapshots__/entity_files_test.ts.snap
+++ b/src/v1/tests/__snapshots__/entity_files_test.ts.snap
@@ -41,13 +41,28 @@ snapshot[`entityFiles > can get a single file 1`] = `
 }
 `;
 
+snapshot[`entityFiles > can upload files from path 1`] = `
+{
+  "files[]": [
+    File {
+      name: "test.pdf",
+      size: 16374,
+      type: "",
+    },
+  ],
+  person_id: "170614434",
+}
+`;
+
 snapshot[`entityFiles > can upload a file 1`] = `
 {
-  file: File {
-    name: "test.pdf",
-    size: 16374,
-    type: "",
-  },
+  "files[]": [
+    File {
+      name: "test.pdf",
+      size: 16374,
+      type: "",
+    },
+  ],
   person_id: "170614434",
 }
 `;
diff --git a/src/v1/tests/entity_files_test.ts b/src/v1/tests/entity_files_test.ts
index 3a1ff25..5e9b963 100644
--- a/src/v1/tests/entity_files_test.ts
+++ b/src/v1/tests/entity_files_test.ts
@@ -11,6 +11,10 @@ import { Affinity } from '../index.ts'
 import { entityFilesUrl } from '../urls.ts'
 import { apiKey, isLiveRun } from './env.ts'
 import { getRawFixture, readFixtureFile } from './get_raw_fixture.ts'
+import * as path from '@std/path'
+import fs from 'node:fs'
+
+const __dirname = path.dirname(path.fromFileUrl(import.meta.url))
 
 const multipartFormDataHeaderMatcher = {
     asymmetricMatch: (headers: Record<string, string>) => {
@@ -67,6 +71,32 @@ describe('entityFiles', () => {
         await assertSnapshot(t, res)
     })
 
+    it('can upload files from path', async (t) => {
+        mock
+            ?.onPost(
+                entityFilesUrl(),
+                createSnapshotBodyMatcher(t),
+                multipartFormDataHeaderMatcher,
+            )
+            .reply(
+                200,
+                { success: true },
+            )
+        const localPath = path.join(
+            __dirname,
+            'fixtures',
+            'entity_files',
+            'test.pdf',
+        )
+        const res = await affinity.entityFiles.upload({
+            person_id: 170614434,
+            files: [
+                localPath,
+            ],
+        })
+        assert(res)
+    })
+
     it('can upload a file', async (t) => {
         mock
             ?.onPost(