make: Added AC_PROG_OBJCXX.
diff --git a/configure.ac b/configure.ac
index fd9a589..e52453c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -9,6 +9,7 @@
 AC_PROG_LIBTOOL
 AC_PROG_CXX
 AM_PROG_CC_C_O
+AC_PROG_OBJCXX
 AC_LANG([C++])
 
 AX_CXX_COMPILE_STDCXX_11(, optional)