diff --git a/src/collection.cpp b/src/collection.cpp
index ed423356..1090f39f 100644
--- a/src/collection.cpp
+++ b/src/collection.cpp
@@ -4499,19 +4499,27 @@ Option<bool> Collection::add_reference_fields(nlohmann::json& doc,
         }
 
         if (nest_ref_doc && !ref_doc.empty()) {
-            auto field_name = alias.empty() ? ref_collection_name : alias;
-            doc[field_name] += ref_doc;
-        } else {
-            if (!alias.empty()) {
-                auto temp_doc = ref_doc;
-                ref_doc.clear();
-                for (const auto &item: temp_doc.items()) {
-                    ref_doc[alias + item.key()] = item.value();
-                }
+            auto key = alias.empty() ? ref_collection_name : alias;
+            if (doc.contains(key) && !doc[key].is_array()) {
+                return Option<bool>(400, "Could not include the reference document of `" + ref_collection_name +
+                                            "` collection. Expected `" + key + "` to be an array. Try " +
+                                            (alias.empty() ? "adding an" : "renaming the") + " alias.");
             }
+
+            doc[key] += ref_doc;
+        } else {
             for (auto ref_doc_it = ref_doc.begin(); ref_doc_it != ref_doc.end(); ref_doc_it++) {
+                auto const& ref_doc_key = ref_doc_it.key();
+                auto const& doc_key = alias + ref_doc_key;
+                if (doc.contains(doc_key) && !doc[doc_key].is_array()) {
+                    return Option<bool>(400, "Could not include the value of `" + ref_doc_key +
+                                             "` key of the reference document of `" + ref_collection_name +
+                                             "` collection. Expected `" + doc_key + "` to be an array. Try " +
+                                             (alias.empty() ? "adding an" : "renaming the") + " alias.");
+                }
+
                 // Add the values of ref_doc as JSON array into doc.
-                doc[ref_doc_it.key()] += ref_doc_it.value();
+                doc[doc_key] += ref_doc_it.value();
             }
         }
     }
diff --git a/test/collection_join_test.cpp b/test/collection_join_test.cpp
index 77d35afa..daee7be7 100644
--- a/test/collection_join_test.cpp
+++ b/test/collection_join_test.cpp
@@ -2078,6 +2078,30 @@ TEST_F(CollectionJoinTest, IncludeExcludeFieldsByReference) {
     ASSERT_EQ(73.5, res_obj["hits"][0]["document"].at("product_price"));
 
     // Add alias using `as`
+    req_params = {
+            {"collection", "Products"},
+            {"q", "soap"},
+            {"query_by", "product_name"},
+            {"filter_by", "$Customers(id:*)"},
+            {"include_fields", "id, $Customers(id :merge)"}
+    };
+    search_op = collectionManager.do_search(req_params, embedded_params, json_res, now_ts);
+    ASSERT_FALSE(search_op.ok());
+    ASSERT_EQ("Could not include the value of `id` key of the reference document of `Customers` collection."
+              " Expected `id` to be an array. Try adding an alias.", search_op.error());
+
+    req_params = {
+            {"collection", "Products"},
+            {"q", "soap"},
+            {"query_by", "product_name"},
+            {"filter_by", "$Customers(id:*)"},
+            {"include_fields", "id, $Customers(id :nest) as id"}
+    };
+    search_op = collectionManager.do_search(req_params, embedded_params, json_res, now_ts);
+    ASSERT_FALSE(search_op.ok());
+    ASSERT_EQ("Could not include the reference document of `Customers` collection."
+              " Expected `id` to be an array. Try renaming the alias.", search_op.error());
+
     req_params = {
             {"collection", "Customers"},
             {"q", "Joe"},