diff --git a/BasiliskII/src/Unix/configure.ac b/BasiliskII/src/Unix/configure.ac
index 1f00108c..fc9e128c 100644
--- a/BasiliskII/src/Unix/configure.ac
+++ b/BasiliskII/src/Unix/configure.ac
@@ -1118,7 +1118,7 @@ fi
 
 dnl Add -fno-strict-aliasing for slirp sources
 if [[ "x$HAVE_GCC30" = "xyes" ]]; then
-  SAVED_CXXFLAGS="$CXXFLAGS"
+  SAVED_CFLAGS="$CFLAGS"
   CFLAGS="$CFLAGS -fno-strict-aliasing"
   AC_CACHE_CHECK([whether the compiler supports -fno-strict-aliasing],
     ac_cv_gcc_no_strict_aliasing, [