diff --git a/app/javascript/flavours/glitch/actions/interactions.js b/app/javascript/flavours/glitch/actions/interactions.js
index da06afadf1..8f515c990c 100644
--- a/app/javascript/flavours/glitch/actions/interactions.js
+++ b/app/javascript/flavours/glitch/actions/interactions.js
@@ -416,7 +416,9 @@ export const addReaction = (statusId, name, url) => (dispatch, getState) => {
     dispatch(addReactionRequest(statusId, name, url));
   }
 
-  api(getState).post(`/api/v1/statuses/${statusId}/react/${name}`).then(() => {
+  // encodeURIComponent is required for the Keycap Number Sign emoji, see:
+  // <https://github.com/glitch-soc/mastodon/pull/1980#issuecomment-1345538932>
+  api(getState).post(`/api/v1/statuses/${statusId}/react/${encodeURIComponent(name)}`).then(() => {
     dispatch(addReactionSuccess(statusId, name));
   }).catch(err => {
     if (!alreadyAdded) {
@@ -448,7 +450,7 @@ export const addReactionFail = (statusId, name, error) => ({
 export const removeReaction = (statusId, name) => (dispatch, getState) => {
   dispatch(removeReactionRequest(statusId, name));
 
-  api(getState).post(`/api/v1/statuses/${statusId}/unreact/${name}`).then(() => {
+  api(getState).post(`/api/v1/statuses/${statusId}/unreact/${encodeURIComponent(name)}`).then(() => {
     dispatch(removeReactionSuccess(statusId, name));
   }).catch(err => {
     dispatch(removeReactionFail(statusId, name, err));
diff --git a/app/javascript/mastodon/actions/interactions.js b/app/javascript/mastodon/actions/interactions.js
index 4f80b933d6..28c728d61e 100644
--- a/app/javascript/mastodon/actions/interactions.js
+++ b/app/javascript/mastodon/actions/interactions.js
@@ -436,7 +436,9 @@ export const addReaction = (statusId, name, url) => (dispatch, getState) => {
     dispatch(addReactionRequest(statusId, name, url));
   }
 
-  api(getState).post(`/api/v1/statuses/${statusId}/react/${name}`).then(() => {
+  // encodeURIComponent is required for the Keycap Number Sign emoji, see:
+  // <https://github.com/glitch-soc/mastodon/pull/1980#issuecomment-1345538932>
+  api(getState).post(`/api/v1/statuses/${statusId}/react/${encodeURIComponent(name)}`).then(() => {
     dispatch(addReactionSuccess(statusId, name));
   }).catch(err => {
     if (!alreadyAdded) {
@@ -468,7 +470,7 @@ export const addReactionFail = (statusId, name, error) => ({
 export const removeReaction = (statusId, name) => (dispatch, getState) => {
   dispatch(removeReactionRequest(statusId, name));
 
-  api(getState).post(`/api/v1/statuses/${statusId}/unreact/${name}`).then(() => {
+  api(getState).post(`/api/v1/statuses/${statusId}/unreact/${encodeURIComponent(name)}`).then(() => {
     dispatch(removeReactionSuccess(statusId, name));
   }).catch(err => {
     dispatch(removeReactionFail(statusId, name, err));