diff --git a/django/contrib/admin/static/admin/js/admin/RelatedObjectLookups.js b/django/contrib/admin/static/admin/js/admin/RelatedObjectLookups.js
index f366f30f7e..fb5db940d6 100644
--- a/django/contrib/admin/static/admin/js/admin/RelatedObjectLookups.js
+++ b/django/contrib/admin/static/admin/js/admin/RelatedObjectLookups.js
@@ -111,7 +111,12 @@
                 option = new Option(newRepr, newId);
                 select.options.add(option);
                 // Update SelectBox cache for related fields.
-                if (window.SelectBox !== undefined && !SelectBox.cache[currentSelect.id]) {
+                if (
+                    window.SelectBox !== undefined
+                    && !SelectBox.cache[currentSelect.id]
+                    // Only if SelectBox is managing that field.
+                    && SelectBox.cache[select.id]
+                ) {
                     SelectBox.add_to_cache(select.id, option);
                     // Sort if there are any groups present
                     if (SelectBox.cache[select.id].some(item => item.group)) {
diff --git a/tests/admin_views/models.py b/tests/admin_views/models.py
index fe127f57d3..2f4e43394a 100644
--- a/tests/admin_views/models.py
+++ b/tests/admin_views/models.py
@@ -1196,3 +1196,7 @@ class CamelCaseModel(models.Model):
 class CamelCaseRelatedModel(models.Model):
     m2m = models.ManyToManyField(CamelCaseModel, related_name="m2m")
     fk = models.ForeignKey(CamelCaseModel, on_delete=models.CASCADE, related_name="fk")
+    # Add another relation that will not participate in filter_horizontal.
+    fk2 = models.ForeignKey(
+        CamelCaseModel, on_delete=models.CASCADE, related_name="fk2"
+    )