diff --git a/cinelerra-5.1/opencv_build b/cinelerra-5.1/opencv_build
index fd029027..fabb8775 100644
--- a/cinelerra-5.1/opencv_build
+++ b/cinelerra-5.1/opencv_build
@@ -49,6 +49,7 @@ jobs:=-j$(shell echo $$(($(cpus) + $(cpus)/2 +2)))
 #opencv4 breaks SIFT/SURF findobj
 CFLAGS += -I$(opencv_prefix)/include/opencv4
 CFLAGS += -I$(opencv_prefix)/include
+CFLAGS += -std=c++11
 
 ifeq ($(src),git)
 $(opencv).src: