--- a/lib/h2s/parse.scm
+++ b/lib/h2s/parse.scm
@@ -329,6 +329,8 @@
       (#/^\}\s*([\w_]+)/ (#f name) (make-enum name (reverse enums))) ; ----->
       ;; empty line:
       (#/^\s*$/ () (loop (read-line) enums))
+      ;; preprocessor directive:
+      (#/^\s*#\s*\w+/ () (loop (read-line) enums))
       ;; 
       (test has-comment? (skip-comment line (cut loop <> enums) err-eof)) ;  what if?:      new_value,  /* boring comment*/
       (#/\s+([\w_]+),?/ (#f enum)