diff --git a/lib/net/http/generic_request.rb b/lib/net/http/generic_request.rb
index 96396b0..6fe5cc5 100644
--- a/lib/net/http/generic_request.rb
+++ b/lib/net/http/generic_request.rb
@@ -410,7 +410,7 @@ def flush_buffer(out, buf, chunked_p)
 
   def wait_for_continue(sock, ver)
     if ver >= '1.1' and @header['expect'] and
-        @header['expect'].include?('100-continue')
+        @header['expect'].any? { |value| value.casecmp?('100-continue') }
       if sock.io.to_io.wait_readable(sock.continue_timeout)
         res = Net::HTTPResponse.read_new(sock)
         unless res.kind_of?(Net::HTTPContinue)