diff --git a/mex/build/matlab/configure.ac b/mex/build/matlab/configure.ac
index 5200c5e841df2ebc4f625a50bccd3b49bff02559..7bb918a99994cce488b6c3b68eacbeaab5b0d2ee 100644
--- a/mex/build/matlab/configure.ac
+++ b/mex/build/matlab/configure.ac
@@ -46,7 +46,7 @@ case ${host_os} in
     CC=gcc-3
     CXX=g++-3
     CFLAGS="$CFLAGS -mno-cygwin"
-    CXXFLAGS="$CFLAGS -mno-cygwin"
+    CXXFLAGS="$CXXFLAGS -mno-cygwin"
     ;;
 esac