diff --git a/app/Http/Controllers/Api/V1/TimeEntryController.php b/app/Http/Controllers/Api/V1/TimeEntryController.php
index 5c44ee50..8cdfa8cb 100644
--- a/app/Http/Controllers/Api/V1/TimeEntryController.php
+++ b/app/Http/Controllers/Api/V1/TimeEntryController.php
@@ -630,7 +630,8 @@ class TimeEntryController extends Controller
      */
     private function storeTimeEntry(Organization $organization, Member $member, TimeEntryStoreRequest $request): JsonResource
     {
-        if ($request->input('end') === null && TimeEntry::query()->whereBelongsTo($member, 'member')->where('end', null)->exists()) {
+        // A user can only have one running time entry, across all organizations
+        if ($request->input('end') === null && TimeEntry::query()->where('user_id', $member->user_id)->whereNull('end')->exists()) {
             throw new TimeEntryStillRunningApiException;
         }
 
diff --git a/tests/Unit/Endpoint/Api/V1/TimeEntryEndpointTest.php b/tests/Unit/Endpoint/Api/V1/TimeEntryEndpointTest.php
index 8d9b349d..459d2d68 100644
--- a/tests/Unit/Endpoint/Api/V1/TimeEntryEndpointTest.php
+++ b/tests/Unit/Endpoint/Api/V1/TimeEntryEndpointTest.php
@@ -2446,6 +2446,31 @@ class TimeEntryEndpointTest extends ApiEndpointTestAbstract
         $response->assertJsonPath('error', true);
     }
 
+    public function test_store_endpoint_fails_if_user_already_has_active_time_entry_in_another_organization(): void
+    {
+        // Arrange
+        $data = $this->createUserWithPermission([
+            'time-entries:create:own',
+        ]);
+        $otherOrganization = Organization::factory()->create();
+        $otherMember = Member::factory()->forOrganization($otherOrganization)->forUser($data->user)->create();
+        TimeEntry::factory()->forOrganization($otherOrganization)->forMember($otherMember)->active()->create();
+        Passport::actingAs($data->user);
+
+        // Act
+        $response = $this->postJson(route('api.v1.time-entries.store', [$data->organization->getKey()]), [
+            'billable' => true,
+            'start' => Carbon::now()->toIso8601ZuluString(),
+            'end' => null,
+            'member_id' => $data->member->getKey(),
+        ]);
+
+        // Assert
+        $response->assertStatus(400);
+        $response->assertJsonPath('key', 'time_entry_still_running');
+        $this->assertSame(0, TimeEntry::query()->whereBelongsTo($data->organization, 'organization')->count());
+    }
+
     public function test_store_endpoint_releases_running_time_entry_lock_after_request(): void
     {
         // Arrange