diff --git a/flow-typed/box-ui-elements.js b/flow-typed/box-ui-elements.js
index e7ed7e29b2..d49631d2d9 100644
--- a/flow-typed/box-ui-elements.js
+++ b/flow-typed/box-ui-elements.js
@@ -231,7 +231,7 @@ type MetadataTemplateField = {
     hidden?: boolean,
     key: string,
     type: string,
-}
+};
 
 type MetadataEditorTemplate = {
     id: string,
@@ -395,7 +395,7 @@ type FolderUploadItem = {
     status: UploadStatus,
     options?: UploadItemAPIOptions,
     isFolder?: boolean,
-}
+};
 
 type UploadItem = {
     api: PlainUploadAPI | MultiputUploadAPI,
@@ -649,7 +649,7 @@ type UploadDataTransferItemWithAPIOptions = {
     options?: UploadItemAPIOptions,
 };
 
-type UploadFile = File & { webkitRelativePath?: string };
+type UploadFile = File & { webkitRelativePath?: string, lastModifiedDate?: Date };
 
 type DirectoryReader = {
     readEntries: (Function, Function) => void,
@@ -691,16 +691,11 @@ type ElementsError = {
 };
 
 type ErrorContextProps = {
-    onError: (
-        error: ElementsXhrError | Error,
-        code: string,
-        contextInfo?: Object,
-        origin: ErrorOrigins,
-    ) => void,
+    onError: (error: ElementsXhrError | Error, code: string, contextInfo?: Object, origin: ErrorOrigins) => void,
 };
 
 type ElementsErrorCallback = (e: ElementsXhrError, code: string, contextInfo?: Object) => void;
 
 type ClassificationInfo = {
-    Box__Security__Classification__Key?: string
+    Box__Security__Classification__Key?: string,
 } & MetadataInstance;
diff --git a/src/util/__tests__/uploads-test.js b/src/util/__tests__/uploads-test.js
index 7e38730e3f..dea1dbe849 100644
--- a/src/util/__tests__/uploads-test.js
+++ b/src/util/__tests__/uploads-test.js
@@ -45,12 +45,17 @@ describe('util/uploads', () => {
         // file with non-numeric lastModified (invalid Date)
         // file no lastModified
         test.each`
-            file                                                      | expectedResult
-            ${{ lastModified: 1483326245678 }}                        | ${'2017-01-02T03:04:05Z'}
-            ${{ lastModified: 'not a number' }}                       | ${null}
-            ${{ lastModified: new Date('2017-01-02T03:04:05.678Z') }} | ${'2017-01-02T03:04:05Z'}
-            ${{ lastModified: new Date('not valid') }}                | ${null}
-            ${{}}                                                     | ${null}
+            file                                                          | expectedResult
+            ${{ lastModified: 1483326245678 }}                            | ${'2017-01-02T03:04:05Z'}
+            ${{ lastModified: 'not a number' }}                           | ${null}
+            ${{ lastModified: new Date('2017-01-02T03:04:05.678Z') }}     | ${'2017-01-02T03:04:05Z'}
+            ${{ lastModified: new Date('not valid') }}                    | ${null}
+            ${{}}                                                         | ${null}
+            ${{ lastModifiedDate: 1483326245678 }}                        | ${'2017-01-02T03:04:05Z'}
+            ${{ lastModifiedDate: 'not a number' }}                       | ${null}
+            ${{ lastModifiedDate: new Date('2017-01-02T03:04:05.678Z') }} | ${'2017-01-02T03:04:05Z'}
+            ${{ lastModifiedDate: new Date('not valid') }}                | ${null}
+            ${{}}                                                         | ${null}
         `(
             'should return the properly formatted date when possible and return null otherwise',
             ({ file, expectedResult }) => {
diff --git a/src/util/uploads.js b/src/util/uploads.js
index 827aab658d..da0a993483 100644
--- a/src/util/uploads.js
+++ b/src/util/uploads.js
@@ -120,14 +120,14 @@ function toISOStringNoMS(date: Date): string {
  * @return {?string}
  */
 function getFileLastModifiedAsISONoMSIfPossible(file: UploadFile): ?string {
+    // The compatibility chart at https://developer.mozilla.org/en-US/docs/Web/API/File/lastModified#Browser_compatibility
+    // is not up to date as of 12-13-2018. Edge & ie11 do not support lastModified, but support lastModifiedDate.
+    const lastModified = file.lastModified || file.lastModifiedDate;
     if (
-        // $FlowFixMe https://github.com/facebook/flow/issues/6131
-        file.lastModified &&
-        (typeof file.lastModified === 'string' ||
-            typeof file.lastModified === 'number' ||
-            file.lastModified instanceof Date)
+        lastModified &&
+        (typeof lastModified === 'string' || typeof lastModified === 'number' || lastModified instanceof Date)
     ) {
-        const lastModifiedDate = new Date(file.lastModified);
+        const lastModifiedDate = new Date(lastModified);
         if (isValidDateObject(lastModifiedDate)) {
             return toISOStringNoMS(lastModifiedDate);
         }