diff --git a/src/components/views/rooms/BasicMessageComposer.js b/src/components/views/rooms/BasicMessageComposer.js
index 770e4766f3..95855e8c81 100644
--- a/src/components/views/rooms/BasicMessageComposer.js
+++ b/src/components/views/rooms/BasicMessageComposer.js
@@ -268,7 +268,7 @@ export default class BasicMessageEditor extends React.Component {
             handled = true;
         // autocomplete or enter to send below shouldn't have any modifier keys pressed.
         } else if (!(event.metaKey || event.altKey || event.shiftKey)) {
-            if (model.autoComplete) {
+            if (model.autoComplete && model.autoComplete.hasCompletions()) {
                 const autoComplete = model.autoComplete;
                 switch (event.key) {
                     case "ArrowUp":
@@ -309,7 +309,11 @@ export default class BasicMessageEditor extends React.Component {
             const position = model.positionForOffset(caret.offset, caret.atNodeEnd);
             const range = model.startRange(position);
             range.expandBackwardsWhile((index, offset, part) => {
-                return part.text[offset] !== " " && (part.type === "plain" || part.type === "pill-candidate");
+                return part.text[offset] !== " " && (
+                    part.type === "plain" ||
+                    part.type === "pill-candidate" ||
+                    part.type === "command"
+                );
             });
             const {partCreator} = model;
             // await for auto-complete to be open
diff --git a/src/editor/autocomplete.js b/src/editor/autocomplete.js
index d3b8f713b9..fe6f3bfe1f 100644
--- a/src/editor/autocomplete.js
+++ b/src/editor/autocomplete.js
@@ -40,6 +40,11 @@ export default class AutocompleteWrapperModel {
         return this._getAutocompleterComponent().hasSelection();
     }
 
+    hasCompletions() {
+        const ac = this._getAutocompleterComponent();
+        return ac && ac.countCompletions() > 0;
+    }
+
     onEnter() {
         this._updateCallback({close: true});
     }
diff --git a/src/editor/parts.js b/src/editor/parts.js
index d14fcf98a2..9ca9205bcd 100644
--- a/src/editor/parts.js
+++ b/src/editor/parts.js
@@ -465,10 +465,6 @@ export class CommandPartCreator extends PartCreator {
 }
 
 class CommandPart extends PillCandidatePart {
-    acceptsInsertion(chr, i) {
-        return PlainPart.prototype.acceptsInsertion.call(this, chr, i);
-    }
-
     get type() {
         return "command";
     }