diff --git a/src/url_aggregator.cpp b/src/url_aggregator.cpp
index c1d06bc5a..2fb1cf5d5 100644
--- a/src/url_aggregator.cpp
+++ b/src/url_aggregator.cpp
@@ -317,7 +317,7 @@ bool url_aggregator::set_pathname(const std::string_view input) {
   }
   clear_pathname();
   parse_path(input);
-  if (checkers::begins_with(input, "//") && !has_authority() &&
+  if (checkers::begins_with(get_pathname(), "//") && !has_authority() &&
       !has_dash_dot()) {
     buffer.insert(components.pathname_start, "/.");
     components.pathname_start += 2;
diff --git a/tests/basic_tests.cpp b/tests/basic_tests.cpp
index 79ccbc667..3cbe75e82 100644
--- a/tests/basic_tests.cpp
+++ b/tests/basic_tests.cpp
@@ -430,4 +430,14 @@ TYPED_TEST(basic_tests, nodejs_undici_2971) {
       out->get_href(),
       R"(https://non-ascii-location-header.sys.workers.dev/%EC%95%88%EB%85%95)");
   SUCCEED();
+}
+
+TYPED_TEST(basic_tests, path_setter_bug) {
+  std::string_view base = "blob:/?";
+  auto base_url = ada::parse<ada::url_aggregator>(base);
+  ASSERT_TRUE(base_url);
+  ASSERT_TRUE(base_url->validate());
+  ASSERT_TRUE(base_url->set_pathname("//.."));
+  ASSERT_TRUE(base_url->validate());
+  SUCCEED();
 }
\ No newline at end of file