diff --git a/unittest/force-styles/tests/angle-cosine_periodic.yaml b/unittest/force-styles/tests/angle-cosine_periodic.yaml
index 5c8227fcbd..ee3e5c1469 100644
--- a/unittest/force-styles/tests/angle-cosine_periodic.yaml
+++ b/unittest/force-styles/tests/angle-cosine_periodic.yaml
@@ -15,7 +15,10 @@ angle_coeff: ! |
   3  50.0 -1 3
   4 100.0 -1 4
 equilibrium: 4 3.141592653589793 3.141592653589793 2.0943951023931957 2.356194490192345
-extract: ! ""
+extract: ! |
+  k 1
+  b 1
+  multiplicity 1
 natoms: 29
 init_energy: 1178.5476942873006
 init_stress: ! |2-