diff --git a/src/components/views/rooms/SendMessageComposer.js b/src/components/views/rooms/SendMessageComposer.js
index c11d940331..c4ae2929af 100644
--- a/src/components/views/rooms/SendMessageComposer.js
+++ b/src/components/views/rooms/SendMessageComposer.js
@@ -24,6 +24,8 @@ import {
     containsEmote,
     stripEmoteCommand,
     unescapeMessage,
+    startsWith,
+    stripPrefix,
 } from '../../../editor/serialize';
 import {CommandPartCreator} from '../../../editor/parts';
 import BasicMessageComposer from "./BasicMessageComposer";
@@ -61,6 +63,9 @@ function createMessageContent(model, permalinkCreator) {
     if (isEmote) {
         model = stripEmoteCommand(model);
     }
+    if (startsWith(model, "//")) {
+        model = stripPrefix(model, "/");
+    }
     model = unescapeMessage(model);
     const repliedToEvent = RoomViewStore.getQuotingEvent();
 
@@ -175,13 +180,13 @@ export default class SendMessageComposer extends React.Component {
         const parts = this.model.parts;
         const firstPart = parts[0];
         if (firstPart) {
-            if (firstPart.type === "command") {
+            if (firstPart.type === "command" && !firstPart.text.startsWith("//")) {
                 return true;
             }
             // be extra resilient when somehow the AutocompleteWrapperModel or
             // CommandPartCreator fails to insert a command part, so we don't send
             // a command as a message
-            if (firstPart.text.startsWith("/") && (firstPart.type === "plain" || firstPart.type === "pill-candidate")) {
+            if (firstPart.text.startsWith("/") && !firstPart.text.startsWith("//") && (firstPart.type === "plain" || firstPart.type === "pill-candidate")) {
                 return true;
             }
         }
diff --git a/src/editor/serialize.js b/src/editor/serialize.js
index a55eed97da..ba380f2809 100644
--- a/src/editor/serialize.js
+++ b/src/editor/serialize.js
@@ -61,18 +61,26 @@ export function textSerialize(model) {
 }
 
 export function containsEmote(model) {
+    return startsWith(model, "/me ");
+}
+
+export function startsWith(model, prefix) {
     const firstPart = model.parts[0];
     // part type will be "plain" while editing,
     // and "command" while composing a message.
     return firstPart &&
         (firstPart.type === "plain" || firstPart.type === "command") &&
-        firstPart.text.startsWith("/me ");
+        firstPart.text.startsWith(prefix);
 }
 
 export function stripEmoteCommand(model) {
     // trim "/me "
+    return stripPrefix(model, "/me ");
+}
+
+export function stripPrefix(model, prefix) {
     model = model.clone();
-    model.removeText({index: 0, offset: 0}, 4);
+    model.removeText({index: 0, offset: 0}, prefix.length);
     return model;
 }