--- Makefile.gnu
+++ Makefile.gnu
@@ -25,7 +25,7 @@
 CFLAGS += $(INCLUDE)
 CXXFLAGS ?= -O3 -fPIC -fexceptions -fvisibility=hidden -Wno-ctor-dtor-privacy
 # LibJXR
-CXXFLAGS += -D__ANSI__
+CXXFLAGS += -D__ANSI__ -std=c++11
 CXXFLAGS += $(INCLUDE)
 
 ifeq ($(shell sh -c 'uname -m 2>/dev/null || echo not'),x86_64)