diff --git a/assembler.cr b/assembler.cr
index fb81401..5859622 100644
--- a/assembler.cr
+++ b/assembler.cr
@@ -36,6 +36,7 @@ OptionParser.parse! do |parser|
     parser.on("-i IPIN", "--inst-pin=IPIN", "select instruction pin") do |ip|
         inst_pin = ip
     end
+    parser.on("-h", "--help") {  puts parser }
 end
 
 enum InstType