diff --git a/src/SlashCommands.tsx b/src/SlashCommands.tsx
index 4a7b37b5e5..9700c57d67 100644
--- a/src/SlashCommands.tsx
+++ b/src/SlashCommands.tsx
@@ -150,6 +150,10 @@ function success(promise?: Promise<any>) {
     return {promise};
 }
 
+function successSync(value: any) {
+    return success(Promise.resolve(value));
+}
+
 /* Disable the "unexpected this" error for these commands - all of the run
  * functions are called with `this` bound to the Command instance.
  */
@@ -160,7 +164,7 @@ export const Commands = [
         args: '<message>',
         description: _td('Sends the given message as a spoiler'),
         runFn: function(roomId, message) {
-            return success(ContentHelpers.makeHtmlMessage(
+            return successSync(ContentHelpers.makeHtmlMessage(
                 message,
                 `<span data-mx-spoiler>${message}</span>`,
             ));
@@ -176,7 +180,7 @@ export const Commands = [
             if (args) {
                 message = message + ' ' + args;
             }
-            return success(ContentHelpers.makeTextMessage(message));
+            return successSync(ContentHelpers.makeTextMessage(message));
         },
         category: CommandCategories.messages,
     }),
@@ -189,7 +193,7 @@ export const Commands = [
             if (args) {
                 message = message + ' ' + args;
             }
-            return success(ContentHelpers.makeTextMessage(message));
+            return successSync(ContentHelpers.makeTextMessage(message));
         },
         category: CommandCategories.messages,
     }),
@@ -202,7 +206,7 @@ export const Commands = [
             if (args) {
                 message = message + ' ' + args;
             }
-            return success(ContentHelpers.makeTextMessage(message));
+            return successSync(ContentHelpers.makeTextMessage(message));
         },
         category: CommandCategories.messages,
     }),
@@ -215,7 +219,7 @@ export const Commands = [
             if (args) {
                 message = message + ' ' + args;
             }
-            return success(ContentHelpers.makeTextMessage(message));
+            return successSync(ContentHelpers.makeTextMessage(message));
         },
         category: CommandCategories.messages,
     }),
@@ -224,7 +228,7 @@ export const Commands = [
         args: '<message>',
         description: _td('Sends a message as plain text, without interpreting it as markdown'),
         runFn: function(roomId, messages) {
-            return success(ContentHelpers.makeTextMessage(messages));
+            return successSync(ContentHelpers.makeTextMessage(messages));
         },
         category: CommandCategories.messages,
     }),
@@ -233,7 +237,7 @@ export const Commands = [
         args: '<message>',
         description: _td('Sends a message as html, without interpreting it as markdown'),
         runFn: function(roomId, messages) {
-            return success(ContentHelpers.makeHtmlMessage(messages, messages));
+            return successSync(ContentHelpers.makeHtmlMessage(messages, messages));
         },
         category: CommandCategories.messages,
     }),
@@ -978,7 +982,7 @@ export const Commands = [
         args: '<message>',
         runFn: function(roomId, args) {
             if (!args) return reject(this.getUserId());
-            return success(ContentHelpers.makeHtmlMessage(args, textToHtmlRainbow(args)));
+            return successSync(ContentHelpers.makeHtmlMessage(args, textToHtmlRainbow(args)));
         },
         category: CommandCategories.messages,
     }),
@@ -988,7 +992,7 @@ export const Commands = [
         args: '<message>',
         runFn: function(roomId, args) {
             if (!args) return reject(this.getUserId());
-            return success(ContentHelpers.makeHtmlEmote(args, textToHtmlRainbow(args)));
+            return successSync(ContentHelpers.makeHtmlEmote(args, textToHtmlRainbow(args)));
         },
         category: CommandCategories.messages,
     }),