diff --git a/include/polyhedron_unary_op.h b/include/polyhedron_unary_op.h
index f8cf7ac..f7589a7 100644
--- a/include/polyhedron_unary_op.h
+++ b/include/polyhedron_unary_op.h
@@ -121,9 +121,7 @@ class polyhedron_multmatrix4 : public polyhedron_unary_op
 {
     private:
         /** @brief matrix to apply */
-        double m_matrix[3][3];
-        /** @brief translation to apply */
-        double m_translation[3];
+        double m_matrix[4][4];
     public:
         /**
          @brief constructor, takes a list of matrix elements as arguments
diff --git a/source/polyhedron_unary_op.cpp b/source/polyhedron_unary_op.cpp
index 3e0223b..b72996d 100644
--- a/source/polyhedron_unary_op.cpp
+++ b/source/polyhedron_unary_op.cpp
@@ -119,30 +119,29 @@ polyhedron_multmatrix4::polyhedron_multmatrix4(
 		const double yx, const double yy, const double yz, const double ya,
 		const double zx, const double zy, const double zz, const double za,
 		const double ax, const double ay, const double az, const double aa ) {
-	m_matrix[0][0] = xx; m_matrix[0][1] = xy; m_matrix[0][2] = xz;
-	m_matrix[1][0] = yx; m_matrix[1][1] = yy; m_matrix[1][2] = yz;
-	m_matrix[2][0] = zx; m_matrix[2][1] = zy; m_matrix[2][2] = zz;
-
-	m_translation[0] = xa;
-	m_translation[1] = ya;
-	m_translation[2] = za;
+	//the last row is effectively ignored
+	m_matrix[0][0] = xx; m_matrix[0][1] = xy; m_matrix[0][2] = xz; m_matrix[0][3] = xa;
+	m_matrix[1][0] = yx; m_matrix[1][1] = yy; m_matrix[1][2] = yz; m_matrix[1][3] = ya;
+	m_matrix[2][0] = zx; m_matrix[2][1] = zy; m_matrix[2][2] = zz; m_matrix[2][3] = za;
+	m_matrix[3][0] = ax; m_matrix[3][1] = ay; m_matrix[3][2] = az; m_matrix[3][3] = aa;
 }
 
 polyhedron polyhedron_multmatrix4::operator()( const polyhedron &in ) {
 	std::vector<double> coords, new_coords;
 	std::vector<int>	faces;
 	in.output_store_in_mesh( coords, faces );
-  new_coords.resize(coords.size());
+    new_coords.resize(coords.size());
 	for( int offset=0; offset<(int)coords.size(); offset+=3 ){
-	for ( int j=0; j<3; j++ ) {
-		for ( int k=0; k<3; k++ ) {
-			new_coords[offset+j] += m_matrix[j][k] * coords[offset+j];
-		}
-	}
+        for ( int j=0; j<3; j++ ) {
+            for ( int k=0; k<4; k++ ) {
+                if (k==3) {
+                    new_coords[offset+j] += m_matrix[j][k]; } // *1 is omitted from the end of this line
+                else {
+                    new_coords[offset+j] += m_matrix[j][k] * coords[offset+k]; }
+            }
+        }
 	}
-  polyhedron_translate* translate = new polyhedron_translate(m_translation[0], m_translation[1], m_translation[2]);
 	polyhedron ret;
 	ret.initialize_load_from_mesh( new_coords, faces );
-  ret = (*translate)(ret);
 	return ret;
 }