diff --git a/lib/debug/server_cdp.rb b/lib/debug/server_cdp.rb
index abc18b6a7..d87f2ca3b 100644
--- a/lib/debug/server_cdp.rb
+++ b/lib/debug/server_cdp.rb
@@ -421,7 +421,7 @@ def extract_data
         first_group = @sock.getbyte
         opcode = first_group & 0b00001111
         raise Detach if opcode == 8
-        raise "Unsupported: #{opcode}" unless opcode == 1
+        raise "Unsupported: #{opcode} #{first_group}" unless opcode == 1
 
         fin = first_group & 0b10000000 != 128
         raise 'Unsupported' if fin