diff --git a/src/api/methods/api-files.ts b/src/api/methods/api-files.ts
index 1d70d8a..eb15c92 100644
--- a/src/api/methods/api-files.ts
+++ b/src/api/methods/api-files.ts
@@ -113,12 +113,17 @@ export class ApiFiles extends ApiBase {
     const { sinceEvent, ...rest } = request;
     const allKeys: Key[] = await this.listKeys({ ...rest, event: true }, config);
 
+    const keysWithEvent = allKeys.filter((key) => key.event !== undefined && key.event !== null);
     const maxEvent: number | null =
-      allKeys.length > 0 ? allKeys.reduce((max, key) => Math.max(max, key.event ?? 0), 0) : null;
+      keysWithEvent.length > 0
+        ? keysWithEvent.reduce((max, key) => Math.max(max, key.event!), -Infinity)
+        : null;
 
     const keys: Key[] =
       sinceEvent !== null && sinceEvent !== undefined
-        ? allKeys.filter((key) => (key.event ?? 0) > sinceEvent)
+        ? allKeys.filter(
+            (key) => key.event !== undefined && key.event !== null && key.event > sinceEvent,
+          )
         : allKeys;
 
     return { keys, maxEvent };
diff --git a/tests/fixtures/full-project/fileKeysWithEvents.json b/tests/fixtures/full-project/fileKeysWithEvents.json
index 24e133d..48d7e4b 100644
--- a/tests/fixtures/full-project/fileKeysWithEvents.json
+++ b/tests/fixtures/full-project/fileKeysWithEvents.json
@@ -5,28 +5,28 @@
       "key": ["app_title"],
       "value": "My Application",
       "vid": -7407901648464613000,
-      "event": 100
+      "event": -6585819442721198000
     },
     {
       "id": "_a0000000000000000002",
       "key": ["welcome_message"],
       "value": "Welcome to My Application!",
       "vid": -7407901648464613000,
-      "event": 200
+      "event": -6585819442721190000
     },
     {
       "id": "_a0000000000000000003",
       "key": ["login_button"],
       "value": "Log In",
       "vid": -7407901648464613000,
-      "event": 200
+      "event": -6585819442721190000
     },
     {
       "id": "_a0000000000000000004",
       "key": ["headers", "role"],
       "value": "Project role",
       "vid": -7407781050279235000,
-      "event": 300
+      "event": -6585819442721180000
     }
   ]
 }
diff --git a/tests/specs/files.spec.ts b/tests/specs/files.spec.ts
index 2c6f559..8f0dab2 100644
--- a/tests/specs/files.spec.ts
+++ b/tests/specs/files.spec.ts
@@ -113,7 +113,7 @@ describe('Files', (): void => {
     });
 
     expect(result.keys.length).toBe(4);
-    expect(result.maxEvent).toBe(300);
+    expect(result.maxEvent).toBe(-6585819442721180000);
   });
 
   test('api.files.listKeysSinceEvent filters keys by sinceEvent', async (): Promise<void> => {
@@ -122,13 +122,13 @@ describe('Files', (): void => {
       project,
       file,
       lang: Locales.ENGLISH,
-      sinceEvent: 100,
+      sinceEvent: -6585819442721198000,
     });
 
-    // Keys with event 200 and 300 (3 keys), excludes event 100
+    // Keys with event > -6585819442721198000 (3 keys), excludes the oldest
     expect(result.keys.length).toBe(3);
-    expect(result.maxEvent).toBe(300);
-    expect(result.keys.every((k) => (k.event ?? 0) > 100)).toBe(true);
+    expect(result.maxEvent).toBe(-6585819442721180000);
+    expect(result.keys.every((k) => k.event! > -6585819442721198000)).toBe(true);
   });
 
   test('api.files.listKeysSinceEvent returns empty keys when sinceEvent >= maxEvent', async (): Promise<void> => {
@@ -137,11 +137,11 @@ describe('Files', (): void => {
       project,
       file,
       lang: Locales.ENGLISH,
-      sinceEvent: 300,
+      sinceEvent: -6585819442721180000,
     });
 
     expect(result.keys.length).toBe(0);
-    expect(result.maxEvent).toBe(300);
+    expect(result.maxEvent).toBe(-6585819442721180000);
   });
 
   test('api.files.getContents', async (): Promise<void> => {