diff --git a/vlib/v/gen/c/index.v b/vlib/v/gen/c/index.v
index 99a7f78165..f57ade3d93 100644
--- a/vlib/v/gen/c/index.v
+++ b/vlib/v/gen/c/index.v
@@ -449,7 +449,10 @@ fn (mut g Gen) index_of_map(node ast.IndexExpr, sym ast.TypeSymbol) {
 			g.write('->val')
 		}
 		g.write(', &(${key_type_str}[]){')
+		old_is_assign_lhs := g.is_assign_lhs
+		g.is_assign_lhs = false
 		g.expr(node.index)
+		g.is_assign_lhs = old_is_assign_lhs
 		g.write('}, &(${elem_type_str}[]){ ${zero} }))')
 	} else {
 		zero := g.type_default(info.value_type)
diff --git a/vlib/v/tests/result_with_index_expr_test.v b/vlib/v/tests/result_with_index_expr_test.v
new file mode 100644
index 0000000000..b11dff2ffd
--- /dev/null
+++ b/vlib/v/tests/result_with_index_expr_test.v
@@ -0,0 +1,25 @@
+import x.json2
+
+struct SomeStruct {
+	title string
+}
+
+fn test_result_with_index() {
+	resp := '{
+  		"userId": 1,
+  		"id": 1,
+  		"title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
+  		"body": "quia et suscipitsuscipit recusandae consequuntur expedita et cumreprehenderit molestiae ut ut quas totamnostrum rerum est autem sunt rem eveniet architecto"
+}'
+	raw_data := json2.raw_decode(resp)!
+
+	data := raw_data as map[string]json2.Any
+
+	mut ss := map[int]SomeStruct{}
+	s := SomeStruct{
+		title: data['title']!.str()
+	}
+	ss[data['id']!.int()] = s
+	t := ss[data['id']!.int()]
+	assert t.title == 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit'
+}