diff --git a/src/slang/physics/kerr_lp_redshift.sl b/src/slang/physics/kerr_lp_redshift.sl
new file mode 100644
index 0000000000000000000000000000000000000000..226f8d761a7c055712d91939927d2b2d38ad30ae
--- /dev/null
+++ b/src/slang/physics/kerr_lp_redshift.sl
@@ -0,0 +1,18 @@
+%!%+
+%\function{kerr_lp_redshift}
+%\synopsis{calculates the redshift from a Lamp Post source (point-like)
+% on the rotational axis of a spining black hole (spin a) to the  observer}
+%\usage{kerr_lp_redshift(height, a)}
+%\description
+%   z_obs = 1 / ( sqrt( 1 - 2*h/(h^2 + a^2) )  - 1 
+%!%-
+define kerr_lp_redshift(){
+   variable height, a;
+   
+   switch(_NARGS)
+   { case 2: (height, a) = ();}
+   { help(_function_name()); return; }
+
+
+   return 1.0 / sqrt( 1.0 - 2*height / (height^2 + a^2))-1.0;
+}
diff --git a/test/test_reflection_fraction_relxill.sl b/test/test_reflection_fraction_relxill.sl
index 819eba3f907288c9ccecdbcc6bf1a8c2dafaba32..f4f970704ddd2ff1f425d285e20d4ed31d474b21 100644
--- a/test/test_reflection_fraction_relxill.sl
+++ b/test/test_reflection_fraction_relxill.sl
@@ -1,12 +1,8 @@
 require("./share/isisscripts.sl");
 
-evalfile("src/fitting/relxill/reflection_fraction_relxill.sl");
-
-
-
 variable CONST_prec = 1e-2;
 
-putenv("RELXILL_TABLE_PATH","");  %% make sure no env variable is set
+putenv("RELXILL_TABLE_PATH=");  %% make sure no env variable is set
 variable path_to_reltable = "/userdata/data/dauser/relline_tables/";
 variable table_name = "rel_lp_table_v0.5b.fits";
 
@@ -34,4 +30,5 @@ if (stat_file(path_to_reltable+table_name)!=NULL){
    exit(all(tests_passed) ? 0 : 1);
 } else {
    message(" skipping tests of reflection_fraction_relxill(), as table could not be found");
+   exit(0);
 }