diff --git a/include/boost/numeric/ublas/config.hpp b/include/boost/numeric/ublas/config.hpp
index b1377fe2..3c62cf75 100644
--- a/include/boost/numeric/ublas/config.hpp
+++ b/include/boost/numeric/ublas/config.hpp
@@ -337,7 +337,9 @@ namespace std {
 #define BOOST_UBLAS_USE_FAST_SAME
 
 // Use expression templates.
+#ifndef BOOST_UBLAS_USE_ET
 #define BOOST_UBLAS_USE_ET
+#endif
 
 // Disable performance options in debug mode
 #else
@@ -352,8 +354,10 @@ namespace std {
 
 #ifdef BOOST_MSVC
 // Use expression templates (otherwise we get many ICE's)
+#ifndef BOOST_UBLAS_USE_ET
 #define BOOST_UBLAS_USE_ET
 #endif
+#endif
 
 // Bounds check
 #define BOOST_UBLAS_BOUNDS_CHECK