diff --git a/bin/gen_api_header.sh b/bin/gen_api_header.sh
index 2b21995..d4e93eb 100755
--- a/bin/gen_api_header.sh
+++ b/bin/gen_api_header.sh
@@ -1,4 +1,4 @@
 #!/bin/env sh
 # single header api generator with clang
 
-clang -I./ -P -E -nostdinc -nobuiltininc -DTWN_NOT_C $TWNROOT/include/twn_game_api.h | clang-format
+clang -I./ -P -E -nostdinc -nobuiltininc -DTWN_NOT_C $TWNROOT/include/twn_game_api.h 2> /dev/null | clang-format