diff --git a/xs/src/libslic3r/TransformationMatrix.cpp b/xs/src/libslic3r/TransformationMatrix.cpp
index 55bc7b6d8..5d739da2e 100644
--- a/xs/src/libslic3r/TransformationMatrix.cpp
+++ b/xs/src/libslic3r/TransformationMatrix.cpp
@@ -68,7 +68,7 @@ void TransformationMatrix::swap(TransformationMatrix &other)
     std::swap(this->m33, other.m33); std::swap(this->m34, other.m34);
 }
 
-float* TransformationMatrix::matrix3x4f()
+float* TransformationMatrix::matrix3x4f() const
 {
     float out_arr[12];
     out_arr[0] = this->m11;  out_arr[1] = this->m12;  out_arr[2] = this->m13;  out_arr[3] = this->m14;
@@ -77,21 +77,24 @@ float* TransformationMatrix::matrix3x4f()
     return out_arr;
 }
 
-double TransformationMatrix::determinante()
+double TransformationMatrix::determinante() const
 {
     // translation elements don't influence the determinante
     // because of the 0s on the other side of main diagonal
     return m11*(m22*m33 - m23*m32) - m12*(m21*m33 - m23*m31) + m13*(m21*m32 - m31*m22);
 }
 
-bool TransformationMatrix::inverse(TransformationMatrix* inverse)
+bool TransformationMatrix::inverse(TransformationMatrix* inverse) const
 {
     // from http://mathworld.wolfram.com/MatrixInverse.html
     // and https://math.stackexchange.com/questions/152462/inverse-of-transformation-matrix
     TransformationMatrix mat;
     double det = this->determinante();
     if (abs(det) < 1e-9)
+    {
+        inverse = &mat;
         return false;
+    }
     double fac = 1.0 / det;
 
     mat.m11 = fac*(this->m22*this->m33 - this->m23*this->m32);
diff --git a/xs/src/libslic3r/TransformationMatrix.hpp b/xs/src/libslic3r/TransformationMatrix.hpp
index 15448f843..796a3d46d 100644
--- a/xs/src/libslic3r/TransformationMatrix.hpp
+++ b/xs/src/libslic3r/TransformationMatrix.hpp
@@ -27,13 +27,13 @@ public:
 
     /// Return the row-major form of the represented transformation matrix
     /// for admesh transform
-    float * matrix3x4f();
+    float * matrix3x4f() const;
 
     /// Return the determinante of the matrix
-    double determinante();
+    double determinante() const;
 
     /// Returns the inverse of the matrix
-    bool inverse(TransformationMatrix * inverse);
+    bool inverse(TransformationMatrix * inverse) const;
 
     /// Perform Translation
     void translate(double x, double y, double z);
diff --git a/xs/xsp/TransformationMatrix.xsp b/xs/xsp/TransformationMatrix.xsp
index 39f956c6f..5d0fba0bb 100644
--- a/xs/xsp/TransformationMatrix.xsp
+++ b/xs/xsp/TransformationMatrix.xsp
@@ -6,60 +6,59 @@
 %}
 
 %name{Slic3r::TransformationMatrix} class TransformationMatrix {
-    TransformationMatrix();
-    ~TransformationMatrix();
-    Clone<TransformationMatrix> clone()
-        %code{% RETVAL = THIS; %};
+   TransformationMatrix();
+   ~TransformationMatrix();
+   Clone<TransformationMatrix> clone()
+      %code{% RETVAL = THIS; %};
         
-    float m11;
-        %code%{ RETVAL = THIS->m11; %}
-    void set_m11(float value)
-        %code%{ THIS->m11 = value; %}
-    float m12;
-        %code%{ RETVAL = THIS->m12; %}
-    void set_m12(float value)
-        %code%{ THIS->m12 = value; %}
-    float m13;
-        %code%{ RETVAL = THIS->m13; %}
-    void set_m13(float value)
-        %code%{ THIS->m13 = value; %}
-    float m14;
-        %code%{ RETVAL = THIS->m14; %}
-    void set_m14(float value)
-        %code%{ THIS->m14 = value; %}
-
-    float m21;
-        %code%{ RETVAL = THIS->m21; %}
-    void set_m21(float value)
-        %code%{ THIS->m21 = value; %}
-    float m22;
-        %code%{ RETVAL = THIS->m22; %}
-    void set_m22(float value)
-        %code%{ THIS->m22 = value; %}
-    float m23;
-        %code%{ RETVAL = THIS->m23; %}
-    void set_m23(float value)
-        %code%{ THIS->m23 = value; %}
-    float m24;
-        %code%{ RETVAL = THIS->m24; %}
-    void set_m24(float value)
-        %code%{ THIS->m24 = value; %}
-
-    float m31;
-        %code%{ RETVAL = THIS->m31; %}
-    void set_m31(float value)
-        %code%{ THIS->m31 = value; %}
-    float m32;
-        %code%{ RETVAL = THIS->m32; %}
-    void set_m32(float value)
-        %code%{ THIS->m32 = value; %}
-    float m33;
-        %code%{ RETVAL = THIS->m33; %}
-    void set_m33(float value)
-        %code%{ THIS->m33 = value; %}
-    float m34;
-        %code%{ RETVAL = THIS->m34; %}
-    void set_m34(float value)
-        %code%{ THIS->m34 = value; %}
+   double m11;
+      %code%{ RETVAL = THIS->m11; %}
+   void set_m11(double value)
+      %code%{ THIS->m11 = value; %}
+   double m12;
+      %code%{ RETVAL = THIS->m12; %}
+   void set_m12(double value)
+      %code%{ THIS->m12 = value; %}
+   double m13;
+      %code%{ RETVAL = THIS->m13; %}
+   void set_m13(double value)
+      %code%{ THIS->m13 = value; %}
+   double m14;
+      %code%{ RETVAL = THIS->m14; %}
+   void set_m14(double value)
+      %code%{ THIS->m14 = value; %}
+   double m21;
+      %code%{ RETVAL = THIS->m21; %}
+   void set_m21(double value)
+      %code%{ THIS->m21 = value; %}
+   double m22;
+      %code%{ RETVAL = THIS->m22; %}
+   void set_m22(double value)
+      %code%{ THIS->m22 = value; %}
+   double m23;
+      %code%{ RETVAL = THIS->m23; %}
+   void set_m23(double value)
+      %code%{ THIS->m23 = value; %}
+   double m24;
+      %code%{ RETVAL = THIS->m24; %}
+   void set_m24(double value)
+      %code%{ THIS->m24 = value; %}
+   double m31;
+      %code%{ RETVAL = THIS->m31; %}
+   void set_m31(double value)
+      %code%{ THIS->m31 = value; %}
+   double m32;
+      %code%{ RETVAL = THIS->m32; %}
+   void set_m32(double value)
+      %code%{ THIS->m32 = value; %}
+   double m33;
+      %code%{ RETVAL = THIS->m33; %}
+   void set_m33(double value)
+      %code%{ THIS->m33 = value; %}
+   double m34;
+      %code%{ RETVAL = THIS->m34; %}
+   void set_m34(double value)
+      %code%{ THIS->m34 = value; %}
         
+
 };