diff --git a/src/hyperlink/_url.py b/src/hyperlink/_url.py
index 8797b5c..b731122 100644
--- a/src/hyperlink/_url.py
+++ b/src/hyperlink/_url.py
@@ -163,6 +163,7 @@ def __nonzero__(self):
     r"|(?P<bad_host>.*?))?"
     r"(?::(?P<port>.*))?$"
 )
+_PORT_RE = re.compile(r"\A[0-9]+\Z")
 
 
 _HEX_CHAR_MAP = dict(
@@ -1407,12 +1408,11 @@ def from_text(cls, text):
         host = au_gs["ipv6_host"] or au_gs["plain_host"]
         port = au_gs["port"]
         if port is not None:
-            try:
-                port = int(port)  # type: ignore[assignment] # FIXME, see below
-            except ValueError:
-                if not port:  # TODO: excessive?
-                    raise URLParseError("port must not be empty: %r" % au_text)
+            if not port:  # TODO: excessive?
+                raise URLParseError("port must not be empty: %r" % au_text)
+            if not _PORT_RE.match(port):
                 raise URLParseError("expected integer for port, not %r" % port)
+            port = int(port)  # type: ignore[assignment] # FIXME, see below
 
         scheme = gs["scheme"] or u""
         fragment = gs["fragment"] or u""
diff --git a/src/hyperlink/test/test_url.py b/src/hyperlink/test/test_url.py
index 37c9172..cead8ae 100644
--- a/src/hyperlink/test/test_url.py
+++ b/src/hyperlink/test/test_url.py
@@ -1114,6 +1114,14 @@ def test_invalid_ipv6(self):
     def test_invalid_port(self):
         # type: () -> None
         self.assertRaises(URLParseError, URL.from_text, "ftp://portmouth:smash")
+        for url_text in [
+            "http://example.com: 11",
+            "http://example.com:+11",
+            "http://example.com:-11",
+            "http://example.com:1_1",
+            u"http://example.com:\u0ed1",
+        ]:
+            self.assertRaises(URLParseError, URL.from_text, url_text)
         self.assertRaises(
             ValueError,
             URL.from_text,