diff --git a/src/documents/serialisers.py b/src/documents/serialisers.py
index 5c90c6f1c..5c71de9a9 100644
--- a/src/documents/serialisers.py
+++ b/src/documents/serialisers.py
@@ -18,6 +18,8 @@ from django.core.exceptions import ValidationError
 from django.core.validators import DecimalValidator
 from django.core.validators import EmailValidator
 from django.core.validators import MaxLengthValidator
+from django.core.validators import MaxValueValidator
+from django.core.validators import MinValueValidator
 from django.core.validators import RegexValidator
 from django.core.validators import integer_validator
 from django.db.models import Count
@@ -875,6 +877,13 @@ class CustomFieldInstanceSerializer(serializers.ModelSerializer):
                 uri_validator(data["value"])
             elif field.data_type == CustomField.FieldDataType.INT:
                 integer_validator(data["value"])
+                try:
+                    value_int = int(data["value"])
+                except (TypeError, ValueError):
+                    raise serializers.ValidationError("Enter a valid integer.")
+                # Keep values within the PostgreSQL integer range
+                MinValueValidator(-2147483648)(value_int)
+                MaxValueValidator(2147483647)(value_int)
             elif (
                 field.data_type == CustomField.FieldDataType.MONETARY
                 and data["value"] != ""
diff --git a/src/documents/tests/test_api_documents.py b/src/documents/tests/test_api_documents.py
index 87190c23b..f40ef157f 100644
--- a/src/documents/tests/test_api_documents.py
+++ b/src/documents/tests/test_api_documents.py
@@ -1664,6 +1664,44 @@ class TestDocumentApi(DirectoriesMixin, DocumentConsumeDelayMixin, APITestCase):
 
         self.consume_file_mock.assert_not_called()
 
+    def test_patch_document_integer_custom_field_out_of_range(self):
+        """
+        GIVEN:
+            - An integer custom field
+            - A document
+        WHEN:
+            - Patching the document with an integer value exceeding PostgreSQL's range
+        THEN:
+            - HTTP 400 is returned (validation catches the overflow)
+            - No custom field instance is created
+        """
+        cf_int = CustomField.objects.create(
+            name="intfield",
+            data_type=CustomField.FieldDataType.INT,
+        )
+        doc = Document.objects.create(
+            title="Doc",
+            checksum="123",
+            mime_type="application/pdf",
+        )
+
+        response = self.client.patch(
+            f"/api/documents/{doc.pk}/",
+            {
+                "custom_fields": [
+                    {
+                        "field": cf_int.pk,
+                        "value": 2**31,  # overflow for PostgreSQL integer fields
+                    },
+                ],
+            },
+            format="json",
+        )
+
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertIn("custom_fields", response.data)
+        self.assertEqual(CustomFieldInstance.objects.count(), 0)
+
     def test_upload_with_webui_source(self):
         """
         GIVEN: A document with a source file