diff --git a/matrix/Matrix.hpp b/matrix/Matrix.hpp
index 86fe51d1af..6c37e63bcd 100644
--- a/matrix/Matrix.hpp
+++ b/matrix/Matrix.hpp
@@ -14,9 +14,14 @@
 #include <string.h>
 #include <math.h>
 
+#include "Vector.hpp"
+
 namespace matrix
 {
 
+template <typename Type, size_t M>
+class Vector;
+
 template<typename Type, size_t  M, size_t N>
 class Matrix
 {
@@ -173,7 +178,7 @@ public:
     Matrix<Type, M, N> operator+(Type scalar) const
     {
         Matrix<Type, M, N> res;
-        Matrix<Type, M, N> &self = *this;
+        const Matrix<Type, M, N> &self = *this;
 
         for (size_t i = 0; i < M; i++) {
             for (size_t j = 0; j < N; j++) {
@@ -265,9 +270,9 @@ public:
         return res;
     }
 
-    Matrix<Type, M, 1> diagonal() const
+    Vector<Type, M> diagonal() const
     {
-        Matrix<Type, M, 1> res;
+        Vector<Type, M> res;
         // force square for now
         const Matrix<Type, M, M> &self = *this;
 
diff --git a/matrix/Vector.hpp b/matrix/Vector.hpp
index ff175d194d..b039b0d10a 100644
--- a/matrix/Vector.hpp
+++ b/matrix/Vector.hpp
@@ -12,6 +12,9 @@
 namespace matrix
 {
 
+template <typename Type, size_t M, size_t N>
+class Matrix;
+
 template<typename Type, size_t M>
 class Vector : public Matrix<Type, M, 1>
 {
@@ -102,12 +105,6 @@ public:
         self = self - other;
     }
 
-    void operator*=(const Vector<Type, M> &other)
-    {
-        Vector<Type, M> &self = *this;
-        self = self * other;
-    }
-
     /**
      * Scalar Operations
      */
@@ -127,7 +124,7 @@ public:
     Vector<Type, M> operator+(Type scalar) const
     {
         Vector<Type, M> res;
-        Vector<Type, M> &self = *this;
+        const Vector<Type, M> &self = *this;
 
         for (size_t i = 0; i < M; i++) {
             res(i) = self(i) + scalar;
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 4c37fe51c9..fe8586b6be 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,3 +1,8 @@
+if (COVERALLS)
+	add_library(coverage
+		coverage.cpp)
+endif()
+
 set(tests
 	setIdentity
 	inverse
diff --git a/test/coverage.cpp b/test/coverage.cpp
index 8a39945119..6246833526 100644
--- a/test/coverage.cpp
+++ b/test/coverage.cpp
@@ -7,7 +7,11 @@
 #include <Scalar.hpp>
 #include <Quaternion.hpp>
 
-template Vector<float, 2>;
-template Euler<float>;
-template Scalar<float>;
-template Matrix<float, 3, 3>;
+namespace matrix {
+
+template class Vector<float, 2>;
+template class Euler<float>;
+template class Scalar<float>;
+template class Matrix<float, 3, 3>;
+
+};