diff --git a/app/stores/DocumentsStore.ts b/app/stores/DocumentsStore.ts
index 2e23f85b3..de8453f7d 100644
--- a/app/stores/DocumentsStore.ts
+++ b/app/stores/DocumentsStore.ts
@@ -1,4 +1,3 @@
-import path from "path";
 import invariant from "invariant";
 import { find, orderBy, filter, compact, omitBy } from "lodash";
 import { observable, action, computed, runInAction } from "mobx";
@@ -14,6 +13,7 @@ import Team from "~/models/Team";
 import env from "~/env";
 import { FetchOptions, PaginationParams, SearchResult } from "~/types";
 import { client } from "~/utils/ApiClient";
+import { extname } from "~/utils/files";
 
 type FetchPageParams = PaginationParams & {
   template?: boolean;
@@ -603,7 +603,7 @@ export default class DocumentsStore extends BaseStore<Document> {
     if (
       file.type &&
       !this.importFileTypes.includes(file.type) &&
-      !this.importFileTypes.includes(path.extname(file.name))
+      !this.importFileTypes.includes(extname(file.name))
     ) {
       throw new Error(`The selected file type is not supported (${file.type})`);
     }
diff --git a/app/utils/files.test.ts b/app/utils/files.test.ts
new file mode 100644
index 000000000..d2b91b55b
--- /dev/null
+++ b/app/utils/files.test.ts
@@ -0,0 +1,12 @@
+import { extname } from "./files";
+
+describe("#extname", () => {
+  test("should extract file extension from string", () => {
+    expect(extname("one.doc")).toBe(".doc");
+    expect(extname("one.test.ts")).toBe(".ts");
+    expect(extname(".DS_Store")).toBe("");
+    expect(extname("directory/one.pdf")).toBe(".pdf");
+    expect(extname("../relative/one.doc")).toBe(".doc");
+    expect(extname(".hidden/directory/one.txt")).toBe(".txt");
+  });
+});
diff --git a/app/utils/files.ts b/app/utils/files.ts
index 564e3393a..6607a6b12 100644
--- a/app/utils/files.ts
+++ b/app/utils/files.ts
@@ -87,3 +87,66 @@ export const dataUrlToBlob = (dataURL: string) => {
   });
   return file;
 };
+
+const CHAR_FORWARD_SLASH = 47; /* / */
+const CHAR_DOT = 46; /* . */
+
+// Based on the NodeJS Library https://github.com/nodejs/node/blob/896b75a4da58a7283d551c4595e0aa454baca3e0/lib/path.js
+// Copyright Joyent, Inc. and other Node contributors.
+export const extname = (path: string) => {
+  if (typeof path !== "string") {
+    throw new TypeError(
+      `The "path" argument must be of type string. Received type ${typeof path}`
+    );
+  }
+
+  let startDot = -1;
+  let startPart = 0;
+  let end = -1;
+  let matchedSlash = true;
+  // Track the state of characters (if any) we see before our first dot and
+  // after any path separator we find
+  let preDotState = 0;
+  for (let i = path.length - 1; i >= 0; --i) {
+    const code = path.charCodeAt(i);
+    if (code === CHAR_FORWARD_SLASH) {
+      // If we reached a path separator that was not part of a set of path
+      // separators at the end of the string, stop now
+      if (!matchedSlash) {
+        startPart = i + 1;
+        break;
+      }
+      continue;
+    }
+    if (end === -1) {
+      // We saw the first non-path separator, mark this as the end of our
+      // extension
+      matchedSlash = false;
+      end = i + 1;
+    }
+    if (code === CHAR_DOT) {
+      // If this is our first dot, mark it as the start of our extension
+      if (startDot === -1) {
+        startDot = i;
+      } else if (preDotState !== 1) {
+        preDotState = 1;
+      }
+    } else if (startDot !== -1) {
+      // We saw a non-dot and non-path separator before our dot, so we should
+      // have a good chance at having a non-empty extension
+      preDotState = -1;
+    }
+  }
+
+  if (
+    startDot === -1 ||
+    end === -1 ||
+    // We saw a non-dot character immediately before the dot
+    preDotState === 0 ||
+    // The (right-most) trimmed path component is exactly '..'
+    (preDotState === 1 && startDot === end - 1 && startDot === startPart + 1)
+  ) {
+    return "";
+  }
+  return path.slice(startDot, end);
+};