diff --git a/lib/libsysdecode/Makefile b/lib/libsysdecode/Makefile
index 60702b613b7c..b13c0f5770d5 100644
--- a/lib/libsysdecode/Makefile
+++ b/lib/libsysdecode/Makefile
@@ -119,10 +119,12 @@ CFLAGS+=-DPF
 # Workaround duplicate declarations in <netinet/ip_compat.h>
 CFLAGS.gcc.ioctl.c+= -Wno-redundant-decls
 
-CFLAGS.gcc+=	${CFLAGS.gcc.${.IMPSRC}}
-
 # Ignore deprecation warning in <sys/pioctl.h>
-CFLAGS.ioctl.c+= -Wno-\#warnings
+CFLAGS.clang.ioctl.c+= -Wno-\#warnings
+CFLAGS.gcc.ioctl.c+= -Wno-cpp
+
+CFLAGS.clang+=	${CFLAGS.clang.${.IMPSRC}}
+CFLAGS.gcc+=	${CFLAGS.gcc.${.IMPSRC}}
 
 DEPENDOBJS+=	tables.h
 tables.h: mktables