diff --git a/doc/faqs/faqs.rst b/doc/faqs/faqs.rst
index 378bb04f..9a3cd2f8 100644
--- a/doc/faqs/faqs.rst
+++ b/doc/faqs/faqs.rst
@@ -20,6 +20,12 @@ the parameters as desired.
 
 .. literalinclude:: plotting_spaghettis.py
 
+x optic does not write a case.pmat file
+---------------------------------------
+Make sure that you set line 6 to "ON" and put a "1" to the following line.
+The "1" is undocumented in Wien2k, but needed to have `case.pmat` written.
+However, we are working on reading directly the `case.mommat2` file.
+
 Why is my calculation not working?
 ----------------------------------
 
diff --git a/doc/guide/transport.rst b/doc/guide/transport.rst
index a0479b7a..030939cd 100644
--- a/doc/guide/transport.rst
+++ b/doc/guide/transport.rst
@@ -65,7 +65,7 @@ The basics steps to calculate the matrix elements of the momentum operator with
     6) Run `x optic`. 
 
 Additionally the input file :file:`case.inop` is required. A detail description on how to setup this file can be found in the Wien2k user guide [#userguide]_ on page 166.
-Here the energy window can be chosen according to the window used for :program:`dmftproj`. However, keep in mind that energies have to be specified in absolute values! Furthermore it is important to set line 6 to ON for printing the matrix elements to the :file:`.pmat` file.
+Here the energy window can be chosen according to the window used for :program:`dmftproj`. However, keep in mind that energies have to be specified in absolute values! Furthermore it is important to set line 6 to "ON" and a "1" in the next line for printing the matrix elements to the :file:`.pmat` file.
 
 
 Using the transport code