diff --git a/etk/math/Matrix2.cpp b/etk/math/Matrix2.cpp
index cb7294a..e5c020a 100644
--- a/etk/math/Matrix2.cpp
+++ b/etk/math/Matrix2.cpp
@@ -152,7 +152,7 @@ etk::Matrix2 etk::Matrix2::operator * (const etk::Matrix2& _obj) {
 	return tmp;
 }
 
-vec2 etk::Matrix2::operator * (const vec2& _obj) {
+vec2 etk::Matrix2::operator * (const vec2& _obj) const {
 	return vec2(_obj.x()*m_mat[0] + _obj.y()*m_mat[1] + m_mat[2],
 	            _obj.x()*m_mat[4] + _obj.y()*m_mat[3] + m_mat[5]);
 }
diff --git a/etk/math/Matrix2.h b/etk/math/Matrix2.h
index f62dfed..838eb4d 100644
--- a/etk/math/Matrix2.h
+++ b/etk/math/Matrix2.h
@@ -77,7 +77,7 @@ namespace etk {
 			 *    * operator
 			 *****************************************************/
 			Matrix2 operator * (const Matrix2& _obj);
-			vec2 operator * (const vec2& _obj);
+			vec2 operator * (const vec2& _obj) const;
 			/*****************************************************
 			 *    ~ operator
 			 *****************************************************/