diff --git a/releng/README b/releng/README
index 2a96097d..3b023653 100644
--- a/releng/README
+++ b/releng/README
@@ -141,8 +141,9 @@ All general options are accepted.
 ./auto_cxx
   Not included in GNU xorriso.
   Exercises inclusion of xorriso/xorriso.h and libisoburn/libisoburn.h
-  in C++ programs and linking of the libraries. It might be necessary
-  to set compiler options by shell variable CFLAGS before running the test.
+  in C++ programs and linking of the libraries. It is possible to override the
+  use of g++ as compiler by shell variable CC. It might be necessary to set
+  compiler options by shell variable CFLAGS before running the test.
   It might be necessary to hand over the install directory of libburn and
   libisofs in shell variable LD_LIBRARY_PATH.
   E.g. if on FreeBSD the include headers libisofs.h , libburn.h are not found:
diff --git a/releng/auto_cxx b/releng/auto_cxx
index 71ed53fe..1086ee4b 100755
--- a/releng/auto_cxx
+++ b/releng/auto_cxx
@@ -29,7 +29,7 @@ fi
 
 # xorriso binary is not needed for that particular test
 SAMPLE_CODE_DIR=codesamples
-CC=g++
+CC=${CC:-g++}
 
 # check compiler
 if ! which "${CC}" >/dev/null 2>&1; then