diff --git a/sis8300llrf.Makefile b/sis8300llrf.Makefile
index cf00edd2b34e0b09135134127bb883a413a24162..b69a8d53124c9731981aae46f0c8dfad206f2b42 100644
--- a/sis8300llrf.Makefile
+++ b/sis8300llrf.Makefile
@@ -61,7 +61,7 @@ endif
 
 # print cc1plus: warning: unrecognized command line option ‘-Wno-format-truncation’ with lower gcc 7
 USR_CFLAGS   += -Wno-format-truncation
-USR_CPPFLAGS += -std=c++11
+USR_CXXFLAGS += -std=c++11
 
 EXCLUDE_ARCHS = linux-ppc64e6500
 EXCLUDE_ARCHS += linux-corei7-poky