diff --git a/src/components/views/rooms/BasicMessageComposer.tsx b/src/components/views/rooms/BasicMessageComposer.tsx
index 7c2eb83a94..d9b34b93ef 100644
--- a/src/components/views/rooms/BasicMessageComposer.tsx
+++ b/src/components/views/rooms/BasicMessageComposer.tsx
@@ -619,13 +619,14 @@ export default class BasicMessageEditor extends React.Component<IProps, IState>
     }
 
     private onFormatAction = (action: Formatting) => {
-        const range = getRangeForSelection(
-            this.editorRef.current,
-            this.props.model,
-            document.getSelection());
+        const range = getRangeForSelection(this.editorRef.current, this.props.model, document.getSelection());
+        // trim the range as we want it to exclude leading/trailing spaces
+        range.trim();
+
         if (range.length === 0) {
             return;
         }
+
         this.historyManager.ensureLastChangesPushed(this.props.model);
         this.modifiedFlag = true;
         switch (action) {
diff --git a/src/editor/range.ts b/src/editor/range.ts
index 27f59f34a9..838dfd8b98 100644
--- a/src/editor/range.ts
+++ b/src/editor/range.ts
@@ -18,6 +18,10 @@ import EditorModel from "./model";
 import DocumentPosition, {Predicate} from "./position";
 import {Part} from "./parts";
 
+const whitespacePredicate: Predicate = (index, offset, part) => {
+    return part.text[offset].trim() === "";
+};
+
 export default class Range {
     private _start: DocumentPosition;
     private _end: DocumentPosition;
@@ -35,6 +39,11 @@ export default class Range {
         });
     }
 
+    trim() {
+        this._start = this._start.forwardsWhile(this.model, whitespacePredicate);
+        this._end = this._end.backwardsWhile(this.model, whitespacePredicate);
+    }
+
     expandBackwardsWhile(predicate: Predicate) {
         this._start = this._start.backwardsWhile(this.model, predicate);
     }
diff --git a/test/editor/range-test.js b/test/editor/range-test.js
index b69ed9eb53..60055af824 100644
--- a/test/editor/range-test.js
+++ b/test/editor/range-test.js
@@ -88,4 +88,19 @@ describe('editor/range', function() {
         expect(model.parts[1].text).toBe("man");
         expect(model.parts.length).toBe(2);
     });
+    it('range trim spaces off both ends', () => {
+        const renderer = createRenderer();
+        const pc = createPartCreator();
+        const model = new EditorModel([
+            pc.plain("abc abc abc"),
+        ], pc, renderer);
+        const range = model.startRange(
+            model.positionForOffset(3, false), // at end of first `abc`
+            model.positionForOffset(8, false), // at start of last `abc`
+        );
+
+        expect(range.parts[0].text).toBe(" abc ");
+        range.trim();
+        expect(range.parts[0].text).toBe("abc");
+    });
 });