diff --git a/lib/net/http/generic_request.rb b/lib/net/http/generic_request.rb
index 003f59d0ac..0b81243064 100644
--- a/lib/net/http/generic_request.rb
+++ b/lib/net/http/generic_request.rb
@@ -143,7 +143,7 @@ class Net::HTTPGenericRequest
     end
 
     if host = self['host']
-      host.sub!(/:.*/s, ''.freeze)
+      host.sub!(/:.*/m, ''.freeze)
     elsif host = @uri.host
     else
      host = addr