diff --git a/PARAM_DEF/psp_bls_da.xml b/PARAM_DEF/psp_bls_da.xml
index 3c51c22..43d51f8 100644
--- a/PARAM_DEF/psp_bls_da.xml
+++ b/PARAM_DEF/psp_bls_da.xml
@@ -4,6 +4,6 @@
 	<get>
 		<amdaParam name="psp_xyz_hee"/>		 
 	</get>
-	<process>RAD2DEG*acos($psp_xyz_hee[0]/sqrt($psp_xyz_hee[0]*$psp_xyz_hee[0]+$psp_xyz_hee[1]*$psp_xyz_hee[1]))*Sign($psp_xyz_hee[1])</process>
+	<process>RAD2DEG*acos($psp_xyz_hee[0]/sqrt($psp_xyz_hee[0]*$psp_xyz_hee[0]+$psp_xyz_hee[1]*$psp_xyz_hee[1]))*Sign(-$psp_xyz_hee[1])</process>
 	<output/>
 </param>
--
libgit2 0.21.2