diff --git a/include/boost/numeric/ublas/matrix_expression.hpp b/include/boost/numeric/ublas/matrix_expression.hpp
index 37238d36..f728b592 100644
--- a/include/boost/numeric/ublas/matrix_expression.hpp
+++ b/include/boost/numeric/ublas/matrix_expression.hpp
@@ -229,7 +229,7 @@ namespace boost { namespace numeric { namespace ublas {
         matrix_reference ():
               e_ (nil_) {}
         BOOST_UBLAS_INLINE
-        matrix_reference (refered_type &e):
+        explicit matrix_reference (refered_type &e):
               e_ (e) {}
 
         // Accessors
@@ -1047,7 +1047,7 @@ namespace boost { namespace numeric { namespace ublas {
         matrix_unary1 ():
             e_ () {}
         BOOST_UBLAS_INLINE
-        matrix_unary1 (const expression_type &e):
+        explicit matrix_unary1 (const expression_type &e):
             e_ (e) {}
 
         // Accessors
@@ -1526,7 +1526,7 @@ namespace boost { namespace numeric { namespace ublas {
         BOOST_UBLAS_INLINE
         // ISSUE may be used as mutable expression.
         // matrix_unary2 (const expression_type &e):
-        matrix_unary2 (expression_type &e):
+        explicit matrix_unary2 (expression_type &e):
             e_ (e) {}
 
         // Accessors
@@ -5175,7 +5175,7 @@ namespace boost { namespace numeric { namespace ublas {
         matrix_scalar_unary ():
             e_ () {}
         BOOST_UBLAS_INLINE
-        matrix_scalar_unary (const expression_type &e):
+        explicit matrix_scalar_unary (const expression_type &e):
             e_ (e) {}
 
 #ifndef BOOST_UBLAS_NESTED_CLASS_DR45
diff --git a/include/boost/numeric/ublas/vector_expression.hpp b/include/boost/numeric/ublas/vector_expression.hpp
index 65b2e397..ab4c885d 100644
--- a/include/boost/numeric/ublas/vector_expression.hpp
+++ b/include/boost/numeric/ublas/vector_expression.hpp
@@ -233,7 +233,7 @@ namespace boost { namespace numeric { namespace ublas {
         vector_reference ():
             e_ (nil_) {}
         BOOST_UBLAS_INLINE
-        vector_reference (refered_type &e):
+        explicit vector_reference (refered_type &e):
             e_ (e) {}
 
         // Accessors
@@ -479,7 +479,7 @@ namespace boost { namespace numeric { namespace ublas {
         BOOST_UBLAS_INLINE
         // ISSUE may be used as mutable expression.
         // vector_unary (const expression_type &e):
-        vector_unary (expression_type &e):
+        explicit vector_unary (expression_type &e):
             e_ (e) {}
 
         // Accessors
@@ -1672,7 +1672,7 @@ namespace boost { namespace numeric { namespace ublas {
         vector_scalar_unary ():
             e_ () {}
         BOOST_UBLAS_INLINE
-        vector_scalar_unary (const expression_type &e):
+        explicit vector_scalar_unary (const expression_type &e):
             e_ (e) {}
 
 #ifndef BOOST_UBLAS_NESTED_CLASS_DR45