diff --git a/src/components/views/elements/PollCreateDialog.tsx b/src/components/views/elements/PollCreateDialog.tsx
index 655215542d..d982cf9004 100644
--- a/src/components/views/elements/PollCreateDialog.tsx
+++ b/src/components/views/elements/PollCreateDialog.tsx
@@ -30,6 +30,7 @@ import Spinner from "./Spinner";
 
 interface IProps extends IDialogProps {
     room: Room;
+    threadId?: string;
 }
 
 interface IState extends IScrollableBaseState {
@@ -103,7 +104,12 @@ export default class PollCreateDialog extends ScrollableBaseModal<IProps, IState
             this.state.options.map(a => a.trim()).filter(a => !!a),
             M_POLL_KIND_DISCLOSED,
         ).serialize();
-        this.matrixClient.sendEvent(this.props.room.roomId, pollEvent.type, pollEvent.content).then(
+        this.matrixClient.sendEvent(
+            this.props.room.roomId,
+            this.props.threadId,
+            pollEvent.type,
+            pollEvent.content,
+        ).then(
             () => this.props.onFinished(true),
         ).catch(e => {
             console.error("Failed to post poll:", e);
diff --git a/src/components/views/rooms/MessageComposerButtons.tsx b/src/components/views/rooms/MessageComposerButtons.tsx
index b6dcad81e6..e659fb069f 100644
--- a/src/components/views/rooms/MessageComposerButtons.tsx
+++ b/src/components/views/rooms/MessageComposerButtons.tsx
@@ -20,6 +20,7 @@ import { M_POLL_START } from "matrix-events-sdk";
 import React, { createContext, ReactElement, useContext } from 'react';
 import { Room } from 'matrix-js-sdk/src/models/room';
 import { MatrixClient } from 'matrix-js-sdk/src/client';
+import { RelationType } from 'matrix-js-sdk/src/@types/event';
 
 import { _t } from '../../../languageHandler';
 import AccessibleTooltipButton from "../elements/AccessibleTooltipButton";
@@ -73,7 +74,7 @@ const MessageComposerButtons: React.FC<IProps> = (props: IProps) => {
             uploadButton(props, roomId),
             showStickersButton(props),
             voiceRecordingButton(props),
-            pollButton(room),
+            pollButton(room, props.relation),
             showLocationButton(props, room, roomId, matrixClient),
         ];
     } else {
@@ -84,7 +85,7 @@ const MessageComposerButtons: React.FC<IProps> = (props: IProps) => {
         moreButtons = [
             showStickersButton(props),
             voiceRecordingButton(props),
-            pollButton(room),
+            pollButton(room, props.relation),
             showLocationButton(props, room, roomId, matrixClient),
         ];
     }
@@ -288,12 +289,13 @@ function voiceRecordingButton(props: IProps): ReactElement {
     );
 }
 
-function pollButton(room: Room): ReactElement {
-    return <PollButton key="polls" room={room} />;
+function pollButton(room: Room, relation?: IEventRelation): ReactElement {
+    return <PollButton key="polls" room={room} relation={relation} />;
 }
 
 interface IPollButtonProps {
     room: Room;
+    relation?: IEventRelation;
 }
 
 class PollButton extends React.PureComponent<IPollButtonProps> {
@@ -319,12 +321,17 @@ class PollButton extends React.PureComponent<IPollButtonProps> {
                 },
             );
         } else {
+            const threadId = this.props.relation.rel_type === RelationType.Thread
+                ? this.props.relation.event_id
+                : null;
+
             Modal.createTrackedDialog(
                 'Polls',
                 'create',
                 PollCreateDialog,
                 {
                     room: this.props.room,
+                    threadId,
                 },
                 'mx_CompoundDialog',
                 false, // isPriorityModal