diff --git a/PARAM_DEF/solo_bls_dsc_da.xml b/PARAM_DEF/solo_bls_dsc_da.xml
index e461920..b2e2b63 100644
--- a/PARAM_DEF/solo_bls_dsc_da.xml
+++ b/PARAM_DEF/solo_bls_dsc_da.xml
@@ -4,6 +4,6 @@
 	<get>
 		<amdaParam name="so_xyz_hee"/>		 
 	</get>
-	<process>RAD2DEG*acos($so_xyz_hee[0]/sqrt($so_xyz_hee[0]*$so_xyz_hee[0]+$so_xyz_hee[1]*$so_xyz_hee[1]))*Sign($so_xyz_hee[1])</process>
+	<process>RAD2DEG*acos($so_xyz_hee[0]/sqrt($so_xyz_hee[0]*$so_xyz_hee[0]+$so_xyz_hee[1]*$so_xyz_hee[1]))*Sign(-$so_xyz_hee[1])</process>
 	<output/>
 </param>
--
libgit2 0.21.2