diff --git a/cinelerra-5.1/configure.ac b/cinelerra-5.1/configure.ac
index f61ef27..c30bab1 100644
--- a/cinelerra-5.1/configure.ac
+++ b/cinelerra-5.1/configure.ac
@@ -7,6 +7,8 @@ AM_PROG_AS
 AC_LANG_CPLUSPLUS
 AC_LANG_C
 AC_PROG_CXX
+AX_CXX_COMPILE_STDCXX_11
+AX_CXX_COMPILE_STDCXX_14
 
 CFG_CFLAGS+=" -fno-omit-frame-pointer -fno-math-errno -fno-signed-zeros"
 CFG_CFLAGS+=" -pthread -Wall"