diff --git a/src/editor/model.ts b/src/editor/model.ts
index 65058c68cb5..78c749c94e5 100644
--- a/src/editor/model.ts
+++ b/src/editor/model.ts
@@ -99,10 +99,10 @@ export default class EditorModel {
 
     private insertPart(index: number, part: Part): void {
         this._parts.splice(index, 0, part);
-        if (this.activePartIdx && this.activePartIdx >= index) {
+        if (this.activePartIdx !== null && this.activePartIdx >= index) {
             ++this.activePartIdx;
         }
-        if (this.autoCompletePartIdx && this.autoCompletePartIdx >= index) {
+        if (this.autoCompletePartIdx !== null && this.autoCompletePartIdx >= index) {
             ++this.autoCompletePartIdx;
         }
     }
@@ -111,12 +111,12 @@ export default class EditorModel {
         this._parts.splice(index, 1);
         if (index === this.activePartIdx) {
             this.activePartIdx = null;
-        } else if (this.activePartIdx && this.activePartIdx > index) {
+        } else if (this.activePartIdx !== null && this.activePartIdx > index) {
             --this.activePartIdx;
         }
         if (index === this.autoCompletePartIdx) {
             this.autoCompletePartIdx = null;
-        } else if (this.autoCompletePartIdx && this.autoCompletePartIdx > index) {
+        } else if (this.autoCompletePartIdx !== null && this.autoCompletePartIdx > index) {
             --this.autoCompletePartIdx;
         }
     }
diff --git a/test/editor/mock.ts b/test/editor/mock.ts
index 931e3cb5b3c..d1fcc45e96a 100644
--- a/test/editor/mock.ts
+++ b/test/editor/mock.ts
@@ -21,7 +21,7 @@ import { Caret } from "../../src/editor/caret";
 import { PillPart, Part, PartCreator } from "../../src/editor/parts";
 import DocumentPosition from "../../src/editor/position";
 
-class MockAutoComplete {
+export class MockAutoComplete {
     public _updateCallback;
     public _partCreator;
     public _completions;
@@ -44,7 +44,7 @@ class MockAutoComplete {
         });
         if (matches.length === 1 && this._part && this._part.text.length > 1) {
             const match = matches[0];
-            let pill;
+            let pill: PillPart;
             if (match.resourceId[0] === "@") {
                 pill = this._partCreator.userPill(match.text, match.resourceId);
             } else {
diff --git a/test/editor/model-test.ts b/test/editor/model-test.ts
index cb475f696b2..89d88c1d38e 100644
--- a/test/editor/model-test.ts
+++ b/test/editor/model-test.ts
@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import EditorModel from "../../src/editor/model";
-import { createPartCreator, createRenderer } from "./mock";
+import { createPartCreator, createRenderer, MockAutoComplete } from "./mock";
 import DocumentOffset from "../../src/editor/offset";
 import { PillPart } from "../../src/editor/parts";
 import DocumentPosition from "../../src/editor/position";
@@ -186,8 +186,7 @@ describe("editor/model", function () {
             expect(model.parts[1].text).toBe("@a");
 
             // this is a hacky mock function
-            // @ts-ignore
-            model.autoComplete.tryComplete(); // see MockAutoComplete
+            (model.autoComplete as unknown as MockAutoComplete).tryComplete();
 
             expect(renderer.count).toBe(2);
             expect((renderer.caret as DocumentPosition).index).toBe(1);
@@ -216,8 +215,7 @@ describe("editor/model", function () {
             expect(model.parts[1].text).toBe("#r");
 
             // this is a hacky mock function
-            // @ts-ignore
-            model.autoComplete.tryComplete(); // see MockAutoComplete
+            (model.autoComplete as unknown as MockAutoComplete).tryComplete();
 
             expect(renderer.count).toBe(2);
             expect((renderer.caret as DocumentPosition).index).toBe(1);
@@ -236,8 +234,7 @@ describe("editor/model", function () {
 
             model.update("hello #r", "insertText", new DocumentOffset(8, true));
             // this is a hacky mock function
-            // @ts-ignore
-            model.autoComplete.tryComplete(); // see MockAutoComplete
+            (model.autoComplete as unknown as MockAutoComplete).tryComplete();
             model.update("hello #riot-dev!!", "insertText", new DocumentOffset(17, true));
 
             expect(renderer.count).toBe(3);
@@ -314,6 +311,45 @@ describe("editor/model", function () {
             expect(model.parts[0].type).toBe("plain");
             expect(model.parts[0].text).toBe("foo@a");
         });
+
+        it("should allow auto-completing multiple times with resets between them", () => {
+            const renderer = createRenderer();
+            const pc = createPartCreator([{ resourceId: "#riot-dev" } as PillPart]);
+            const model = new EditorModel([pc.plain("")], pc, renderer);
+
+            model.update("#r", "insertText", new DocumentOffset(8, true));
+
+            expect(renderer.count).toBe(1);
+            expect((renderer.caret as DocumentPosition).index).toBe(0);
+            expect((renderer.caret as DocumentPosition).offset).toBe(2);
+            expect(model.parts.length).toBe(1);
+            expect(model.parts[0].type).toBe("pill-candidate");
+            expect(model.parts[0].text).toBe("#r");
+
+            // this is a hacky mock function
+            (model.autoComplete as unknown as MockAutoComplete).tryComplete();
+
+            expect(renderer.count).toBe(2);
+            expect((renderer.caret as DocumentPosition).index).toBe(0);
+            expect((renderer.caret as DocumentPosition).offset).toBe(9);
+            expect(model.parts.length).toBe(1);
+            expect(model.parts[0].type).toBe("room-pill");
+            expect(model.parts[0].text).toBe("#riot-dev");
+
+            model.reset([]);
+            model.update("#r", "insertText", new DocumentOffset(8, true));
+
+            expect(model.parts.length).toBe(1);
+            expect(model.parts[0].type).toBe("pill-candidate");
+            expect(model.parts[0].text).toBe("#r");
+
+            // this is a hacky mock function
+            (model.autoComplete as unknown as MockAutoComplete).tryComplete();
+
+            expect(model.parts.length).toBe(1);
+            expect(model.parts[0].type).toBe("room-pill");
+            expect(model.parts[0].text).toBe("#riot-dev");
+        });
     });
     describe("emojis", function () {
         it("regional emojis should be separated to prevent them to be converted to flag", () => {