diff --git a/src/components/views/rooms/MessageComposer.tsx b/src/components/views/rooms/MessageComposer.tsx
index ebc8d3711c..d126a7b161 100644
--- a/src/components/views/rooms/MessageComposer.tsx
+++ b/src/components/views/rooms/MessageComposer.tsx
@@ -136,7 +136,7 @@ class UploadButton extends React.Component<IUploadButtonProps> {
         this.uploadInput.current.click();
     }
 
-    private onUploadFileInputChange = (ev) => {
+    private onUploadFileInputChange = (ev: React.ChangeEvent<HTMLInputElement>) => {
         if (ev.target.files.length === 0) return;
 
         // take a copy so we can safely reset the value of the form control