diff --git a/src/specify_cli/catalogs.py b/src/specify_cli/catalogs.py
index 774aaa51d7..00c875ca27 100644
--- a/src/specify_cli/catalogs.py
+++ b/src/specify_cli/catalogs.py
@@ -74,6 +74,11 @@ def _validate_catalog_url(cls, url: str) -> None:
         try:
             parsed = urlparse(url)
             hostname = parsed.hostname
+            # Accessing ``port`` performs urllib's syntax/range validation;
+            # ``hostname`` alone does not, so a non-numeric or out-of-range
+            # port would otherwise pass validation here and escape as a raw
+            # http.client.InvalidURL at fetch time.
+            _ = parsed.port
         except ValueError:
             raise cls._error(f"Catalog URL is malformed: {url}") from None
         is_localhost = hostname in ("localhost", "127.0.0.1", "::1")
diff --git a/tests/integrations/test_integration_catalog.py b/tests/integrations/test_integration_catalog.py
index 2e9706e77d..40c777ff15 100644
--- a/tests/integrations/test_integration_catalog.py
+++ b/tests/integrations/test_integration_catalog.py
@@ -116,12 +116,15 @@ def test_hostless_url_with_truthy_netloc_rejected(self, url):
         [
             "https://[::1",                 # unclosed ipv6 bracket
             "https://[not-an-ip]/c.json",   # bracketed non-ip host
+            "https://example.com:notaport/c.json",  # non-numeric port
+            "https://example.com:65536/c.json",     # out-of-range port
         ],
     )
     def test_malformed_url_rejected_cleanly(self, url):
-        # A malformed authority makes urlparse/hostname raise ValueError. The
-        # validator must turn that into its normal catalog error, not leak a
-        # raw ValueError to the caller.
+        # A malformed authority makes urlparse/hostname raise ValueError, and a
+        # bad port makes ``parsed.port`` raise it. The validator must turn that
+        # into its normal catalog error, not leak a raw ValueError to the caller
+        # (or, for a bad port, accept the URL and fail later at fetch time).
         with pytest.raises(IntegrationCatalogError, match="malformed"):
             IntegrationCatalog._validate_catalog_url(url)