diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc
index 0cbd67a81b7..15c3b004d0f 100644
--- a/lib/libc/sys/Makefile.inc
+++ b/lib/libc/sys/Makefile.inc
@@ -134,12 +134,14 @@ NOTE_GNU_STACK=''
 .endif
 
 ${SASM}:
-	printf '#include "compat.h"\n' > ${.TARGET}
+	printf '/* %sgenerated by libc/sys/Makefile.inc */\n' @ > ${.TARGET}
+	printf '#include "compat.h"\n' >> ${.TARGET}
 	printf '#include "SYS.h"\nRSYSCALL(${.PREFIX})\n' >> ${.TARGET}
 	printf  ${NOTE_GNU_STACK} >>${.TARGET}
 
 ${SPSEUDO}:
-	printf '#include "compat.h"\n' > ${.TARGET}
+	printf '/* %sgenerated by libc/sys/Makefile.inc */\n' @ > ${.TARGET}
+	printf '#include "compat.h"\n' >> ${.TARGET}
 	printf '#include "SYS.h"\nPSEUDO(${.PREFIX:S/_//})\n' \
 	    >> ${.TARGET}
 	printf ${NOTE_GNU_STACK} >>${.TARGET}