diff --git a/src/url.cpp b/src/url.cpp
index f35625bed..f7fa85197 100644
--- a/src/url.cpp
+++ b/src/url.cpp
@@ -782,12 +782,9 @@ bool url::set_port(const std::string_view input) {
     port = std::nullopt;
     return true;
   }
-  // Input should not start with control characters.
-  if (ada::unicode::is_c0_control_or_space(trimmed.front())) {
-    return false;
-  }
-  // Input should contain at least one ascii digit.
-  if (input.find_first_of("0123456789") == std::string_view::npos) {
+
+  // Input should not start with a non-digit character.
+  if (!ada::unicode::is_ascii_digit(trimmed.front())) {
     return false;
   }
 
diff --git a/src/url_aggregator.cpp b/src/url_aggregator.cpp
index 08211436d..b6151013a 100644
--- a/src/url_aggregator.cpp
+++ b/src/url_aggregator.cpp
@@ -285,12 +285,9 @@ bool url_aggregator::set_port(const std::string_view input) {
     clear_port();
     return true;
   }
-  // Input should not start with control characters.
-  if (ada::unicode::is_c0_control_or_space(trimmed.front())) {
-    return false;
-  }
-  // Input should contain at least one ascii digit.
-  if (input.find_first_of("0123456789") == std::string_view::npos) {
+
+  // Input should not start with a non-digit character.
+  if (!ada::unicode::is_ascii_digit(trimmed.front())) {
     return false;
   }
 
diff --git a/tests/basic_tests.cpp b/tests/basic_tests.cpp
index d1d452a42..33dc7f966 100644
--- a/tests/basic_tests.cpp
+++ b/tests/basic_tests.cpp
@@ -462,4 +462,17 @@ TYPED_TEST(basic_tests, negativeport) {
   auto url = ada::parse<TypeParam>("https://www.google.com");
   ASSERT_FALSE(url->set_port("-1"));
   SUCCEED();
-}
\ No newline at end of file
+}
+
+// https://github.com/ada-url/ada/issues/826
+TYPED_TEST(basic_tests, set_invalid_port) {
+  auto url = ada::parse<TypeParam>("fake://dummy.test");
+  ASSERT_TRUE(url);
+  ASSERT_FALSE(url->set_port("invalid80"));
+  ASSERT_EQ(url->get_port(), "");
+  ASSERT_TRUE(url->set_port("80valid"));
+  ASSERT_TRUE(url->is_valid);
+  ASSERT_EQ(url->get_port(), "80");
+  ASSERT_TRUE(url->is_valid);
+  SUCCEED();
+}