diff --git a/nselib/http.lua b/nselib/http.lua
index dde9f0fb2..67878e384 100644
--- a/nselib/http.lua
+++ b/nselib/http.lua
@@ -187,6 +187,12 @@ local function get_host_field(host, port, scheme)
   if host_header then return host_header end
   -- If there's no host, we can't invent a name.
   if not host then return nil end
+  -- If there's no port, just return hostname.
+  if not port then return stdnse.get_hostname(host) end
+  if type(port) == "string" then
+    port = tonumber(port)
+    assert(port, "Invalid port: not a number or table")
+  end
   if type(port) == "number" then
     port = {number=port, protocol="tcp"}
   end