diff --git a/frigate/config/config.py b/frigate/config/config.py
index 6873e6b880..db450ffcf3 100644
--- a/frigate/config/config.py
+++ b/frigate/config/config.py
@@ -708,6 +708,14 @@ class FrigateConfig(FrigateBaseModel):
             detector_config.model = model
             self.detectors[key] = detector_config
 
+        # If the top-level model is unset, adopt the first detector's resolved
+        # model so worker processes (which receive self.model) agree with the
+        # dimensions used to size the detection shared memory in start_detectors.
+        if not self.model.model_dump(exclude_unset=True, warnings="none") and self.detectors:
+            first_detector = next(iter(self.detectors.values()))
+            if first_detector.model is not None:
+                self.model = first_detector.model
+
         for name, camera in self.cameras.items():
             modified_global_config = global_config.copy()
 
diff --git a/frigate/test/test_config.py b/frigate/test/test_config.py
index c63f27430a..1469924b9c 100644
--- a/frigate/test/test_config.py
+++ b/frigate/test/test_config.py
@@ -964,8 +964,11 @@ class TestConfig(unittest.TestCase):
             },
         }
 
+        # With no model defined, the top-level model adopts the default
+        # detector's resolved model (openvino + ssdlite_mobilenet_v2 with the
+        # coco_91cl_bkgr labelmap, which has __background__ at index 0).
         frigate_config = FrigateConfig(**config)
-        assert frigate_config.model.merged_labelmap[0] == "person"
+        assert frigate_config.model.merged_labelmap[1] == "person"
 
     def test_default_labelmap(self):
         config = {